Soluble hybrid Fcγ receptors and related methods

ABSTRACT

Disclosed are soluble hybrid Fcγ receptor (FcγR) polypeptide compositions and related methods of using such polypeptides to treat IgG-mediated and immune complex-mediated inflammation. Also disclosed are related compositions and methods for producing the soluble hybrid FcγR polypeptides.

BACKGROUND OF THE INVENTION

Immune system diseases are significant health-care problems that aregrowing at epidemic proportions. As such, they require novel, aggressiveapproaches to the development of new therapeutic agents. Standardtherapy for autoimmune disease has been high dose, long-term systemiccorticosteroids and immunosuppressive agents. The drugs used fall intothree major categories: (1) glucocorticoids, such as prednisone andprednisolone; (2) calcineurin inhibitors, such as cyclosporine andtacrolimus; and (3) antiproliferative/antimetabolic agents such asazathioprine, sirolimus, and mycophenolate mofetil. Although these drugshave met with high clinical success in treating a number of autoimmuneconditions, such therapies require lifelong use and act nonspecificallyto suppress the entire immune system. The patients are thus exposed tosignificantly higher risks of infection and cancer. The calcineurininhibitors and steroids are also nephrotoxic and diabetogenic, which haslimited their clinical utility (Haynes and Fauci in Harrison'sPrinciples of Internal Medicine, 16^(th) edition, Kasper et al., eds(2005), pp 1907-2066).

In addition to the conventional therapies for autoimmune disease,monoclonal antibodies and soluble receptors that target cytokines andtheir receptors have shown efficacy in a variety of autoimmune andinflammation diseases such as rheumatoid arthritis, organtransplantation, and Crohn's disease. Some of the agents includeinfliximab (REMICADE®) and etanercept (ENBREL®) that target tumornecrosis factor (TNF), muromonab-CD3 (ORTHOCLONE OKT3) that targets theT cell antigen CD3, and daclizumab (ZENAPAX®) that binds to CD25 onactivated T cells, inhibiting signaling through this pathway. Whileefficacious in treating certain inflammatory conditions, use of thesedrugs has been limited by side effects including the “cytokine releasesyndrome” and an increased risk of infection (Krensky et al., in Goodmanand Gilman's The Pharmacological Basis of Therapeutics, 10^(th) edition,Hardman and Limbird, eds, (2001), pp 1463-1484).

Passive immunization with intravenous immunoglobulin (IVIG) was licensedin the United States in 1981 for replacement therapy in patients withprimary antibody deficiencies. Subsequent investigation showed that IVIGwas also effective in ameliorating autoimmune symptoms in Kawasaki'sdisease and immune thrombocytopenia purpura (Lemieux et al., Mol.Immunol., 42:839-848, 2005; Ibanez and Montoro-Ronsano Curr. Pharm.Biotech., 4:239-247, 2003; Clynes, J. Clin. Invest., 115:25-27, 2005).IVIG has also been shown to reduce inflammation in adultdermatomyositis, Guillian-Barre syndrome, chronic inflammatorydemyelinating polyneuropathies, multiple sclerosis, vasculitis, uveitis,myasthenia gravis, and in the Lambert-Eaton syndrome (Lemieux et al.,supra; Ibanez and Montoro-Ronsano, supra).

IVIG is obtained from the plasma of large numbers (10,000-20,000) ofhealthy donors by cold ethanol fractionation. Commonly used IVIGpreparations include Sandoglobulin, Flebogamma, Gammagard, Octagam, andVigam S. In general, efficacy is seen when only large amounts of IVIGare infused into a patient, with an average dose of 2 g/kg/month used inautoimmune disease. The common (1-10% of patients) side effects of IVIGtreatment include flushing, fever, myalgia, back pain, headache, nausea,vomiting, arthralgia, and dizziness. Uncommon (0.1-1% of patients) sideeffects include anaphylaxis, aseptic meningitis, acute renal failure,haemolytic anemia, and eczema. Although IVIG is generally consideredsafe, the pooled human plasma source is considered to be a risk factorfor transfer of infectious agents. Thus, the use of IVIG is limited byits availability, high cost ($100/gm, including infusion cost), and thepotential for severe adverse reactions (Lemieux et al., supra; Ibanezand Montoro-Ronsano, supra; Clynes, J. Clin. Invest., 115:25-27, 2005).

Numerous mechanisms have been proposed to explain the mode of action ofIVIG, including regulation of Fc gamma receptor expression, increasedclearance of pathogenic antibodies due to saturation of the neonatal Fcreceptor FcRn, attenuation of complement-mediated damage, and modulationof T and B cells or the reticuloendothelial system (Clynes, supra).Since Fc domains purified from IVIG are as active as intact IgG in anumber of in vitro and in vivo models of inflammation, it is wellaccepted that the anti-inflammatory properties of IVIG reside in the Fcdomain of the IgG (Debre et al., Lancet, 342:945-949, 1993) or asialylated subfraction (Kaneko et al., Science, 313:670-673, 2006).

Fc receptors for IgG (FcγR) play a unique role in mammalian biology byacting as a bridge between the innate and the acquired immune systems(Dijstelbloem et al., Trends Immunol. 22:510-516, 2001; Takai, Nature 2:580-592, 2002; Nimmerjahn and Ravetch, Immunity 24: 19-28, 2006). Byvirtue of their binding to the Fc region of IgG (Woof and Burton, NatureRev. Immunol., 4:1-11, 2004), FcγR regulate a variety of effectorfunctions in ADCC, complement-mediated cell lysis, type IIIhypersensitivity reactions, tolerance, phagocytosis, antigenpresentation, and the processing and clearance of immune complexes(Dijstelbloem et al., supra; Takai, supra; Nimmerjahn and Ravetch,supra).

The FcγR comprise three major gene families in humans including FcγRI(CD64), FcγRII (CD32), and FcγRIII (CD16) (Dijstelbloem et al., supra;Takai, supra). FcγRI is a high affinity receptor for monomeric IgG(10⁸-10⁹ M⁻¹) where FcγRII and FcγRIII exhibit low affinities formonomeric IgG (10⁷ M⁻¹) but bind to IgG immune complexes with greatlyincreased avidities. The FcγRII subfamily is composed of two majorclasses of genes, FcγRIIa and FcγRIIb, which after binding IgG transmitopposing signals to the cell interior. FcγRIIa contains animmunoreceptor tyrosine-activating motif (ITAM) within its shortcytoplasmic tail, while FcγRIIIb transmits inhibitory signals through animmunoreceptor tyrosine inhibitory motif (ITIM) within its cytoplasmicdomain. FcγRIII subfamily also contains two distinct receptor genes,FcγRIIIa and FcγRIIIb. FcγRIIIa is a heterodimeric signaling receptorthat after binding IgG immune complexes transmits activating signalsthrough its associated ITAM-containing common γ chain. FcγRIIIb is boundto the cell membrane through a GPI linker and lacks intrinsic signalingcapacity. FcγRI also lacks an intrinsic signaling capacity but similarto FcγRIIIa, associates with the common γ chain to transmit activatingsignals upon Fc binding. Signaling through FcγR involves kinase mediatedphosphorylation/dephosphorylation events within the ITAM/ITIM sequences(Dacron, Intern. Rev. Immunol., 16: 1-27, 1997).

Consistent with their reported roles in immune biology, the human FcγRexhibit different affinities for subclasses of monomeric IgG: FcγRIbinds IgG1≧IgG3>IgG4>>IgG2; FcγRIIa binds IgG3≧IgG1, IgG2>>IgG4; FcγRIIbbinds IgG3≧IgG1>IgG4>IgG2; FcγRIIIa and FcγRIIIb bind IgG1, IgG3>>IgG2,IgG4 (Dijstelbloem et al., supra; Takai, supra).

In addition to differences in structure and signaling capacities, theFcγR also exhibit differences in cellular expression patterns. Inhumans, FcγRI is expressed predominantly on macrophages, monocytes, andneutrophils but can also be found on eosinophils and dendritic cells.FcγRIIa is the most widely expressed FcγR in humans and is expressed onplatelets, macrophages, neutrophils, eosinophils, dendritic cells andLangerhans cells. FcγRIIb is the only FcγR expressed on B cells but isalso expressed by mast cells, basophils, macrophages, eosinophils,neutrophils, dendritic and langerhan cells. FcγRIIIa is the only FcγRexpressed on human NK cells and is widely expressed, found onmacrophages, monocytes, mast cells, eosinophils, dendritic and langerhancells. The expression of FcγRIIIb, on the other hand is largelyrestricted to neutrophils and eosinophils (Dijstelbloem et al., supra;Takai, supra).

Mice express FcγR that function similarly to the receptors in humanssuch as the orthologs of human high affinity FcγRI and the inhibitoryreceptor FcγRIIb (Nimmerjahn and Ravetch, Immunity, 24:19-28, 2006). Themurine orthologs of human FcγRIIa and IIIa are thought to be FcγRII andFcγRIV, respectively. Mice do not appear to express FcγRIIIb (Nimmerjahnand Ravetch, supra). Although some differences in cellular expressionpatterns have been noted, FcγR gene expression in humans and theirorthologs in mice are generally similar.

Gene targeting in mice has suggested the importance of FcγR in themammalian immune system (see generally Dijstelbloem et al., supra;Takai, supra; Nimmerjahn and Ravetch, supra). Deletion of the common γchain, the signaling subunit of FcγRI, FcγRIII, and FcγRIV, abolishessignaling through all activating FcγR and renders mice resistant to avariety of autoimmune and inflammatory conditions. Mice deficient in theγ-chain exhibit attenuated immune complex-alveolitis, vasculitis,glomerulonephritis, Arthus reaction, and autoimmune hemolytic anemia.Similar data have been described for deletion of the α-chains of FcγRIIand FcγRI. FcγRIII−/− mice exhibit reduced immune complex-inducedalveolitis, reduced sensitivity to autoimmune hemolytic anemia and anattenuated Arthus reaction. FcγRI−/− mice show impaired phagocyticfunction of macrophages, decreased cytokine release, attenuated ADCC andantigen presentation, reduced arthritis, enhanced antibody responses,and impaired hypersensitivity. Deletion of the inhibitory receptor,FcγRIIb, in contrast, results in augmented inflammation and autoimmuneresponses. FcγRIIb−/− mice show enhanced collagen-induced arthritis,spontaneous development of glomerulonephritis on a C57BL/6 background,enhanced Arthus reaction, enhanced alveolitis, enhanced IgG-inducedsystemic anaphylaxis, and enhanced anti-GBM induced glomerulonephritis.Thus, the FcγR play key roles in immune system homeostasis.

There is a need for Fc receptor antagonists, including FcγRIantagonsists, useful in treating a variety of autoimmune diseases.Specifically, such antagonists would function to regulate the immune andhematopoietic systems, since disturbances of such regulation may beinvolved in disorders relating to inflammation, hemostasis, arthritis,immunodeficiency, and other immune and hematopoietic system anomalies.Therefore, there is a need for identification and characterization ofsuch antagonists that can be used to prevent, ameliorate, or correctsuch disorders.

BRIEF SUMMARY OF THE INVENTION

In one aspect, the present invention provides a soluble hybrid Fcγreceptor (FcγR) polypeptide comprising an amino acid sequence that is atleast 70%, at least 80%, at least 90%, at least 95%, at least 96%, atleast 97%, at least 98%, or at least 99% or more identical to amino acidresidues 35-301, 36-301, or 39-301 of SEQ ID NO:40; amino acid residues43-310 or 48-310 of SEQ ID NO:42; amino acid residues 18-286, 21-286, or24-286 of SEQ ID NO:44; or amino acid residues 18-286, 21-286, or 24-286of SEQ ID NO:46, wherein the isolated polypeptide is capable ofspecifically binding to the Fc domain of IgG (e.g., human IgG such as,for example, human IgG1). As described herein, soluble hybrid FcγRpolypeptides of the invention are capable of neutralizing IgG- orimmune-complex-mediated signaling in immune cells. In some embodiments,the hybrid FcγR polypeptide comprises amino acid residues 35-301,36-301, 39-301, 1-301, 35-311, 36-311, 39-311, or 1-311 of SEQ ID NO:40;amino acid residues 43-310, 48-310, 1-310, 43-320, 48-320, or 1-320 ofSEQ ID NO:42; amino acid residues 18-286, 21-286, 24-286, 1-286, 18-296,21-296, 24-296, or 1-296 of SEQ ID NO:44; or amino acid residues 18-286,21-286, 24-286, 1-286, 18-296, 21-296, 24-296, or 1-296 of SEQ ID NO:46.

In another aspect, the present invention provides an isolatedpolynucleotide that encodes a soluble hybrid FcγR polypeptide asdescribed herein. Generally, an isolated polynucleotide of the inventionencodes a soluble FcγR polypeptide comprising an amino acid sequencethat is at least 70%, at least 80%, at least 90%, at least 95%, at least96%, at least 97%, at least 98%, or at least 99% or more identical toamino acid residues 35-301, 36-301, or 39-301 of SEQ ID NO:40; aminoacid residues 43-310 or 48-310 of SEQ ID NO:42; amino acid residues18-286, 21-286, or 24-286 of SEQ ID NO:44; or amino acid residues18-286, 21-286, or 24-286 of SEQ ID NO:46, wherein the encodedpolypeptide is capable of specifically binding to the Fc domain of IgG(e.g., human IgG such as, for example, human IgG1). In some embodiments,the encoded polypeptide comprises amino acid residues 35-301, 36-301, or39-301, 1-301, 35-311, 36-311, 39-311, or 1-311 of SEQ ID NO:40; aminoacid residues 43-310, 48-310, 1-310, 43-320, 48-320, or 1-320 of SEQ IDNO:42; amino acid residues 18-286, 21-286, 24-286, 1-286, 18-296,21-296, 24-296, or 1-296 of SEQ ID NO:44; or amino acid residues 18-286,21-286, 24-286, 1-286, 18-296, 21-296, 24-296, or 1-296 of SEQ ID NO:46.In specific variations, the nucleic acid comprises nucleotide residues103-903, 106-903, 115-903, 1-903, 103-933, 106-933, 115-933, or 1-933 ofSEQ ID NO:39; nucleotide residues 127-930, 142-930, 1-930, 127-960,142-960, or 1-960 of SEQ ID NO:41; nucleotide residues 52-858, 61-858,70-858, 1-858, 52-888, 61-888, 70-888, or 1-888 of SEQ ID NO:43; ornucleotide residues 52-858, 61-858, 70-858, 1-858, 52-888, 61-888,70-888, or 1-888 of SEQ ID NO:45.

Within another aspect, the present invention provides an expressionvector comprising the following operably linked elements: (a) atranscription promoter; a first DNA segment encoding a soluble FcγRpolypeptide comprising an amino acid sequence that is at least 70%, atleast 80%, at least 90%, at least 95%, at least 96%, at least 97%, atleast 98%, or at least 99% or more identical to amino acid residues35-301, 36-301, or 39-301 of SEQ ID NO:40; amino acid residues 43-310 or48-310 of SEQ ID NO:42; amino acid residues 18-286, 21-286, 24-286 ofSEQ ID NO:44; or amino acid residues 18-286, 21-286, or 24-286 of SEQ IDNO:46, wherein the encoded polypeptide is capable of specificallybinding to the Fc domain of IgG (e.g., human IgG such as, for example,human IgG1); and a transcription terminator. In certain embodiments, theexpression vector disclosed above further comprises a secretory signalsequence operably linked to the first DNA segment (e.g., a DNA sequenceencoding amino acid residues 1-34 or 1-35 of SEQ ID NO:40, amino acidresidues 1-42 of SEQ ID NO:42, amino acid residues 1-17 or 1-20 of SEQID NO:44; amino acid residues 1-17 or 1-20 of SEQ ID NO:46, amino acidresidues 1-35 of SEQ ID NO:60, amino acid residues 1-16 of SEQ ID NO:62,amino acid residues 1-19 of SEQ ID NO:64, or amino acid residues 1-23 ofSEQ ID NO:66). In some embodiments, the encoded polypeptide comprisesamino acid residues 35-301, 36-301, 39-301, 1-301, 35-311, 36-311,39-311, or 1-311 of SEQ ID NO:40; amino acid residues 43-310, 48-310,1-310, 43-320, 48-320, or 1-320 of SEQ ID NO:42; amino acid residues18-286, 21-286, 24286, 1-286, 18-296, 21-296, 24-296, or 1-296 of SEQ IDNO:44; amino acid residues 18-286, 21-286, 24-286, 1-286, 18-296,21-296, 24-296, or 1-296 of SEQ ID NO:46; amino acid residues 36-301 or1-301 of SEQ ID NO:60; or amino acid residues 24-289 or 1-289 of SEQ IDNO:66. In specific variations, the DNA segment encoding the polypeptidecomprises nucleotide residues 103-903, 106-903, 115-903, 1-903, 103-933,106-933, 115-933, or 1-933 of SEQ ID NO:39; nucleotide residues 127-930,142-930, 1-930, 127-960, 142-960, or 1-960 of SEQ ID NO:41; nucleotideresidues 52-858, 61-858, 70-858, 1-858, 52-888, 61-888, 70-888, or 1-888of SEQ ID NO:43; nucleotide residues 52-858, 61-858, 70-858, 1-858,52-888, 61-888, 70-888, or 1-888 of SEQ ID NO:45; nucleotide residues106-903 or 1-903 of SEQ ID NO:59; or nucleotide residues 70-867 or 1-867of SEQ ID NO:65.

Within another aspect, the present invention provides a cultured cellcomprising an expression vector as disclosed above, wherein the cellexpresses the soluble FcγR polypeptide encoded by the DNA segments. Inanother embodiment, the cultured cell is as disclosed above, wherein thecell secretes a soluble FcγR polypeptide. In another embodiment, thecultured cell is as disclosed above, wherein the cell secretes a solubleFcγR polypeptide that binds IgG or antagonizes IgG activity, where theIgG is present in a monomeric form or as a multimeric immune complex. Inparticular variations, the cultured cell is a mammalian cell such as,for example, a Chinese Hamster ovary (CHO) cell.

Within another aspect, the present invention provides a method ofproducing a soluble hybrid FcγR polypeptide comprising the followingsteps: (a) culturing a cell as disclosed above; and (b) isolating thesoluble FcγR polypeptide produced by the cell. In some embodiments, themethod comprises culturing a cell into which has been introduced anexpression vector as above, wherein the cell expresses the polypeptideencoded by the DNA segment, and recovering the expressed polypeptide. Incertain variations, the expression vector further includes a secretorysignal sequence operably linked to the DNA segment, wherein the cellexpresses the polypeptide encoded by the DNA segment, and wherein thepolypeptide is secreted from the cell and recovered.

Within another aspect, the present invention provides pharmaceuticalcompositions comprising a pharmaceutically acceptable carrier and asoluble hybrid FcγR polypeptide of the invention.

Within another aspect, the present invention also provides fusionproteins comprising a soluble hybrid FcγR polypeptide and a heterologouspolypeptide segment. Particularly suitable heterologous polypeptidesegments include immunoglobulin moieties. In certain variations, theimmunoglobulin moiety is an immunoglobulin heavy chain constant region,such as a human Fc fragment. The present invention further includesisolated nucleic acid molecules that encode such fusion proteins.

Within another aspect, the present invention provides a method forinhibiting IgG- or immune complex-induced proliferation of hematopoieticcells and hematopoietic cell progenitors comprising culturing bonemarrow or peripheral blood cells with a composition comprising an amountof soluble FcγR sufficient to reduce proliferation of the hematopoieticcells in the bone marrow or peripheral blood cells as compared to bonemarrow or peripheral blood cells cultured in the absence of solublereceptor. In one embodiment, the method is as disclosed above, whereinthe hematopoietic cells and hematopoietic progenitor cells are lymphoidcells. In one embodiment, the method is as disclosed above, wherein thelymphoid cells are macrophages, B cells, or T cells. Within anotheraspect, the present invention provides a method for inhibiting antigenpresentation by cells of the myeloid lineage such as macrophages ormonocytes with a composition comprising an amount of soluble FcγRsufficient to reduce antigen presentation by myeloid-derived cells. Inanother embodiment, the method is as disclosed wherein the cells are Bcells.

Within another aspect, the present invention provides a method ofreducing IgG-mediated or immune-complex-mediated inflammation comprisingadministering to a mammal with inflammation an amount of a compositionof a soluble FcγR sufficient to reduce inflammation.

Within another aspect, the present invention provides a method ofsuppressing an immune response in a mammal comprising administering acomposition comprising a soluble FcγR polypeptide in an acceptablepharmaceutical vehicle.

Moreover, blocking the interaction between cell surface FcγR and the IgGFc domains of immune complexes would attenuate the cellular response tothe immune complexes and thus reduce inflammation. As such, the solubleFcγR polypeptides of the present invention, which as shown herein areeffective in blocking IgG- and immune-complex-mediated immune responses,are useful in therapeutic treatment of inflammatory diseases such as,for example, arthritis (e.g., rheumatoid arthritis or psoriaticarthritis), adult respiratory disease (ARD), endotoxemia, septic shock,multiple organ failure, inflammatory lung injury (e.g., asthma orbronchitis), bacterial pneumonia, psoriasis, eczema, atopic and contactdermatitis, inflammatory bowel disease (IBD) (e.g., ulcerative colitisor Crohn's disease), and aberrant immune responses to bacterial or viralinfection.

These and other aspects of the invention will become evident uponreference to the following detailed description. In addition, variousreferences are identified herein are incorporated by reference in theirentirety.

DEFINITIONS

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art pertinent to the methods and compositions described. As usedherein, the following terms and phrases have the meanings ascribed tothem unless specified otherwise.

As used herein, “nucleic acid” or “nucleic acid molecule” refers topolynucleotides, such as deoxyribonucleic acid (DNA) or ribonucleic acid(RNA), oligonucleotides, fragments generated by the polymerase chainreaction (PCR), and fragments generated by any of ligation, scission,endonuclease action, and exonuclease action. Nucleic acid molecules canbe composed of monomers that are naturally-occurring nucleotides (suchas DNA and RNA), or analogs of naturally-occurring nucleotides (e.g.,α-enantiomeric forms of naturally-occurring nucleotides), or acombination of both. Modified nucleotides can have alterations in sugarmoieties and/or in pyrimidine or purine base moieties. Sugarmodifications include, for example, replacement of one or more hydroxylgroups with halogens, alkyl groups, amines, and azido groups, or sugarscan be functionalized as ethers or esters. Moreover, the entire sugarmoiety can be replaced with sterically and electronically similarstructures, such as aza-sugars and carbocyclic sugar analogs. Examplesof modifications in a base moiety include alkylated purines andpyrimidines, acylated purines or pyrimidines, or other well-knownheterocyclic substitutes. Nucleic acid monomers can be linked byphosphodiester bonds or analogs of such linkages. Analogs ofphosphodiester linkages include phosphorothioate, phosphorodithioate,phosphoroselenoate, phosphorodiselenoate, phosphoroanilothioate,phosphoranilidate, phosphoramidate, and the like. The term “nucleic acidmolecule” also includes so-called “peptide nucleic acids,” whichcomprise naturally-occurring or modified nucleic acid bases attached toa polyamide backbone. Nucleic acids can be either single stranded ordouble stranded.

The term “complement of a nucleic acid molecule” refers to a nucleicacid molecule having a complementary nucleotide sequence and reverseorientation as compared to a reference nucleotide sequence.

The term “degenerate nucleotide sequence” denotes a sequence ofnucleotides that includes one or more degenerate codons as compared to areference nucleic acid molecule that encodes a polypeptide. Degeneratecodons contain different triplets of nucleotides, but encode the sameamino acid residue (i.e., GAU and GAC triplets each encode Asp).

The term “structural gene” refers to a nucleic acid molecule that istranscribed into messenger RNA (mRNA), which is then translated into asequence of amino acids characteristic of a specific polypeptide.

An “isolated nucleic acid molecule” is a nucleic acid molecule that isnot integrated in the genomic DNA of an organism. For example, a DNAmolecule that encodes a growth factor that has been separated from thegenomic DNA of a cell is an isolated DNA molecule. Another example of anisolated nucleic acid molecule is a chemically-synthesized nucleic acidmolecule that is not integrated in the genome of an organism. A nucleicacid molecule that has been isolated from a particular species issmaller than the complete DNA molecule of a chromosome from thatspecies.

A “nucleic acid molecule construct” is a nucleic acid molecule, eithersingle- or double-stranded, that has been modified through humanintervention to contain segments of nucleic acid combined and juxtaposedin an arrangement not existing in nature.

“Linear DNA” denotes non-circular DNA molecules having free 5′ and 3′ends. Linear DNA can be prepared from closed circular DNA molecules,such as plasmids, by enzymatic digestion or physical disruption.

“Complementary DNA (cDNA)” is a single-stranded DNA molecule that isformed from an mRNA template by the enzyme reverse transcriptase.Typically, a primer complementary to portions of mRNA is employed forthe initiation of reverse transcription. Those skilled in the art alsouse the term “cDNA” to refer to a double-stranded DNA moleculeconsisting of such a single-stranded DNA molecule and its complementaryDNA strand. The term “cDNA” also refers to a clone of a cDNA moleculesynthesized from an RNA template.

A “promoter” is a nucleotide sequence that directs the transcription ofa structural gene. Typically, a promoter is located in the 5′ non-codingregion of a gene, proximal to the transcriptional start site of astructural gene. Sequence elements within promoters that function in theinitiation of transcription are often characterized by consensusnucleotide sequences. These promoter elements include RNA polymerasebinding sites, TATA sequences, CAAT sequences, differentiation-specificelements (DSEs; McGehee et al., Mol. Endocrinol. 7:551 (1993)), cyclicAMP response elements (CREs), serum response elements (SREs; Treisman,Seminars in Cancer Biol. 1:47 (1990)), glucocorticoid response elements(GREs), and binding sites for other transcription factors, such asCRE/ATF (O'Reilly et al., J. Biol. Chem. 267:19938 (1992)), AP2 (Ye etal., J. Biol. Chem. 269:25728 (1994)), SP1, cAMP response elementbinding protein (CREB; Loeken, Gene Expr. 3:253 (1993)) and octamerfactors (see, in general, Watson et al., eds., Molecular Biology of theGene, 4th ed. (The Benjamin/Cummings Publishing Company, Inc. 1987), andLemaigre and Rousseau, Biochem. J. 303:1 (1994)). If a promoter is aninducible promoter, then the rate of transcription increases in responseto an inducing agent. In contrast, the rate of transcription is notregulated by an inducing agent if the promoter is a constitutivepromoter. Repressible promoters are also known.

A “core promoter” contains essential nucleotide sequences for promoterfunction, including the TATA box and start of transcription. By thisdefinition, a core promoter may or may not have detectable activity inthe absence of specific sequences that may enhance the activity orconfer tissue specific activity.

A “regulatory element” is a nucleotide sequence that modulates theactivity of a core promoter. For example, a regulatory element maycontain a nucleotide sequence that binds with cellular factors enablingtranscription exclusively or preferentially in particular cells,tissues, or organelles. These types of regulatory elements are normallyassociated with genes that are expressed in a “cell-specific,”“tissue-specific,” or “organelle-specific” manner.

An “enhancer” is a type of regulatory element that can increase theefficiency of transcription, regardless of the distance or orientationof the enhancer relative to the start site of transcription.

“Heterologous DNA” refers to a DNA molecule, or a population of DNAmolecules, that does not exist naturally within a given host cell. DNAmolecules heterologous to a particular host cell may contain DNA derivedfrom the host cell species (i.e., endogenous DNA) so long as that hostDNA is combined with non-host DNA (i.e., exogenous DNA). For example, aDNA molecule containing a non-host DNA segment encoding a polypeptideoperably linked to a host DNA segment comprising a transcriptionpromoter is considered to be a heterologous DNA molecule. Conversely, aheterologous DNA molecule can comprise an endogenous gene operablylinked with an exogenous promoter. As another illustration, a DNAmolecule comprising a gene derived from a wild-type cell is consideredto be heterologous DNA if that DNA molecule is introduced into a mutantcell that lacks the wild-type gene.

A “polypeptide” is a polymer of amino acid residues joined by peptidebonds, whether produced naturally or synthetically. Polypeptides of lessthan about 10 amino acid residues are commonly referred to as“peptides.”

In the polypeptide context, the term “fragment” refers to a portion of apolypeptide typically having at least 20 contiguous or at least 50contiguous amino acids of the polypeptide. A “variant” includes apolypeptide or fragment thereof having amino acid substitutions (e.g.,conservative amino acid substitutions) relative to a second polypeptide;or a polypeptide or fragment thereof that is modified by covalentattachment of a second molecule such as, e.g., by attachment of aheterologous polypeptide, or by glycosylation, acetylation,phosphorylation, and the like. Further included within the definition of“polypeptide” is, for example, polypeptides containing one or moreanalogs of an amino acid (e.g., unnatural amino acids and the like),polypeptides with unsubstituted linkages, as well as other modificationsknown in the art, both naturally and non-naturally occurring.

A “protein” is a macromolecule comprising one or more polypeptidechains. A protein may also comprise non-peptidic components, such ascarbohydrate groups. Carbohydrates and other non-peptidic substituentsmay be added to a protein by the cell in which the protein is produced,and will vary with the type of cell. Proteins are defined herein interms of their amino acid backbone structures; substituents such ascarbohydrate groups are generally not specified, but may be presentnonetheless.

A peptide or polypeptide encoded by a non-host DNA molecule is a“heterologous” peptide or polypeptide.

A “cloning vector” is a nucleic acid molecule, such as a plasmid,cosmid, or bacteriophage, that has the capability of replicatingautonomously in a host cell. Cloning vectors typically contain one or asmall number of restriction endonuclease recognition sites that allowinsertion of a nucleic acid molecule in a determinable fashion withoutloss of an essential biological function of the vector, as well asnucleotide sequences encoding a marker gene that is suitable for use inthe identification and selection of cells transformed with the cloningvector. Marker genes typically include genes that provide tetracyclineresistance or ampicillin resistance.

An “expression vector” is a nucleic acid molecule encoding a gene thatis expressed in a host cell. Typically, an expression vector comprises atranscription promoter, a gene, and a transcription terminator. Geneexpression is usually placed under the control of a promoter, and such agene is said to be “operably linked to” the promoter. Similarly, aregulatory element and a core promoter are operably linked if theregulatory element modulates the activity of the core promoter.

A “recombinant host” is a cell that contains a heterologous nucleic acidmolecule, such as a cloning vector or expression vector. In the presentcontext, an example of a recombinant host is a cell that produces asoluble hybrid FcγR from an expression vector.

“Integrative transformants” are recombinant host cells, in whichheterologous DNA has become integrated into the genomic DNA of thecells.

A “fusion protein” is a hybrid protein expressed by a nucleic acidmolecule comprising nucleotide sequences of at least two genes. Forexample, a fusion protein can comprise at least part of an FcγRpolypeptide fused with a polypeptide that binds an affinity matrix. Sucha fusion protein provides a means to isolate large quantities of FcγRIAusing affinity chromatography.

The term “receptor” denotes a cell-associated protein that binds to abioactive molecule termed a “ligand.” This interaction mediates theeffect of the ligand on the cell. Receptors can be membrane bound,cytosolic or nuclear, monomeric (e.g., thyroid stimulating hormonereceptor, beta-adrenergic receptor) or multimeric (e.g., PDGF receptor,growth hormone receptor, IL-3 receptor, GM-CSF receptor, G-CSF receptor,erythropoietin receptor and IL-6 receptor). Membrane-bound receptors arecharacterized by a multi-domain structure comprising an extracellularligand-binding domain and an intracellular effector domain that istypically involved in signal transduction. In certain membrane-boundreceptors, the extracellular ligand-binding domain and the intracellulareffector domain are located in separate polypeptides that comprise thecomplete functional receptor.

In general, the binding of ligand to receptor results in aconformational change in the receptor that causes an interaction betweenthe effector domain and other molecule(s) in the cell, which in turnleads to an alteration in the metabolism of the cell. Metabolic eventsthat are often linked to receptor-ligand interactions include genetranscription, phosphorylation, dephosphorylation, increases in cyclicAMP production, mobilization of cellular calcium, mobilization ofmembrane lipids, cell adhesion, hydrolysis of inositol lipids andhydrolysis of phospholipids.

A “soluble receptor” is a receptor polypeptide that is not bound to acell membrane. Soluble receptors are most commonly ligand-bindingreceptor polypeptides that lack transmembrane and cytoplasmic domains,and other linkage to the cell membrane such as via glycophosphoinositol(gpi). Soluble receptors can comprise additional amino acid residues,such as affinity tags that provide for purification of the polypeptideor provide sites for attachment of the polypeptide to a substrate, orimmunoglobulin constant region sequences. Many cell-surface receptorshave naturally occurring, soluble counterparts that are produced byproteolysis or translated from alternatively spliced mRNAs. Solublereceptors can be monomeric, homodimeric, heterodimeric, or multimeric,with multimeric receptors generally not comprising more than 9 subunits,preferably not comprising more than 6 subunits, and most preferably notcomprising more than 3, subunits. Receptor polypeptides are said to besubstantially free of transmembrane and intracellular polypeptidesegments when they lack sufficient portions of these segments to providemembrane anchoring or signal transduction, respectively. Moreover, oneof skill in the art using the genetic code can readily determinepolynucleotides that encode such soluble receptor polyptides.

The term “secretory signal sequence” denotes a DNA sequence that encodesa peptide (a “secretory peptide”) that, as a component of a largerpolypeptide, directs the larger polypeptide through a secretory pathwayof a cell in which it is synthesized. The larger polypeptide is commonlycleaved to remove the secretory peptide during transit through thesecretory pathway.

An “isolated polypeptide” is a polypeptide that is essentially free fromcontaminating cellular components, such as carbohydrate, lipid, or otherproteinaceous impurities associated with the polypeptide in nature.Typically, a preparation of isolated polypeptide contains thepolypeptide in a highly purified form, i.e., at least about 80% pure, atleast about 90% pure, at least about 95% pure, greater than 95% pure,such as 96%, 97%, or 98% or more pure, or greater than 99% pure. One wayto show that a particular protein preparation contains an isolatedpolypeptide is by the appearance of a single band following sodiumdodecyl sulfate (SDS)-polyacrylamide gel electrophoresis of the proteinpreparation and Coomassie Brilliant Blue staining of the gel. However,the term “isolated” does not exclude the presence of the samepolypeptide in alternative physical forms, such as dimers oralternatively glycosylated or derivatized forms.

The terms “amino-terminal” and “carboxyl-terminal” are used herein todenote positions within polypeptides. Where the context allows, theseterms are used with reference to a particular sequence or portion of apolypeptide to denote proximity or relative position. For example, acertain sequence positioned carboxyl-terminal to a reference sequencewithin a polypeptide is located proximal to the carboxyl terminus of thereference sequence, but is not necessarily at the carboxyl terminus ofthe complete polypeptide.

The term “expression” refers to the biosynthesis of a gene product. Forexample, in the case of a structural gene, expression involvestranscription of the structural gene into mRNA and the translation ofmRNA into one or more polypeptides.

The term “splice variant” is used herein to denote alternative forms ofRNA transcribed from a gene. Splice variation arises naturally throughuse of alternative splicing sites within a transcribed RNA molecule, orless commonly between separately transcribed RNA molecules, and mayresult in several mRNAs transcribed from the same gene. Splice variantsmay encode polypeptides having altered amino acid sequence. The termsplice variant is also used herein to denote a polypeptide encoded by asplice variant of an mRNA transcribed from a gene.

As used herein, the term “immunomodulator” includes cytokines, stem cellgrowth factors, lymphotoxins, co-stimulatory molecules, hematopoieticfactors, and the like, as well as synthetic analogs of these molecules.

As used herein, a “therapeutic agent” is a molecule or atom which isconjugated to an antibody moiety to produce a conjugate which is usefulfor therapy. Examples of therapeutic agents include drugs, toxins,immunomodulators, chelators, boron compounds, photoactive agents ordyes, and radioisotopes.

A “detectable label” is a molecule or atom which can be conjugated to anantibody moiety to produce a molecule useful for diagnosis. Examples ofdetectable labels include chelators, photoactive agents, radioisotopes,fluorescent agents, paramagnetic ions, or other marker moieties.

The term “affinity tag” is used herein to denote a polypeptide segmentthat can be attached to a second polypeptide to provide for purificationor detection of the second polypeptide or provide sites for attachmentof the second polypeptide to a substrate. In principal, any peptide orprotein for which an antibody or other specific binding agent isavailable can be used as an affinity tag. Affinity tags include apoly-histidine tract, protein A (Nilsson et al., EMBO J. 4:1075 (1985);Nilsson et al., Methods Enzymol. 198:3 (1991)), glutathione Stransferase (Smith and Johnson, Gene 67:31 (1988)), Glu-Glu affinity tag(Grussenmeyer et al., Proc. Natl. Acad. Sci. USA 82:7952 (1985)),substance P, FLAG peptide (Hopp et al., Biotechnology 6:1204 (1988)),streptavidin binding peptide, or other antigenic epitope or bindingdomain. See generally Ford et al., Protein Expression and Purification2:95 (1991). DNA molecules encoding affinity tags are available fromcommercial suppliers (e.g., Pharmacia Biotech, Piscataway, N.J.).

In the context of Fcγ receptor polypeptides or polypeptide regions,“correspondence” to another sequence (e.g., regions, fragments,nucleotide or amino acid positions, or the like) is based on theconvention of numbering according to nucleotide or amino acid positionnumber and then aligning the sequences in a manner that maximizes thepercentage of sequence identity. Because not all positions within agiven “corresponding region” need be identical, non-matching positionswithin a corresponding region may be regarded as “correspondingpositions.” Accordingly, as used herein, referral to an “amino acidposition corresponding to amino acid position [X]” of a specified Fcγreceptor protein represents, in addition to referral to amino acidpositions of the specified Fcγ receptor protein, referral to acollection of equivalent positions in other recognized Fcγ receptorproteins and structural homologues and families.

The terms “identical” or “percent identity,” in the context of two ormore nucleic acids or polypeptide sequences, refer to two or moresequences or subsequences that are the same or have a specifiedpercentage of nucleotides or amino acid residues that are the same(e.g., at least 60% identity, optionally at least 65%, at least 70%, atleast 75%, at least 80%, at least 85%, at least 90%, or at least 95%identity over a specified region), when compared and aligned for maximumcorrespondence over a comparison window, or designated region asmeasured using one of the following sequence comparison algorithms or bymanual alignment and visual inspection. Sequences are “substantiallyidentical” to each other if they are at least 70%, at least 80%, atleast 90%, at least 95%, at least 96%, at least 97%, at least 98%, or atleast 99% identical. These definitions also refer to the complement of atest sequence. Optionally, the identity exists over a region that is atleast about 50 nucleotides in length, or more typically over a regionthat is 100 to 500 or 1000 or more nucleotides in length.

Sequence comparisons can be performed using standard software programssuch as those included in the LASERGENE bioinformatics computing suite,which is produced by DNASTAR (Madison, Wis.). Other methods forcomparing two nucleotide or amino acid sequences by determining optimalalignment are well-known to those of skill in the art. (See, e.g.,Peruski and Perusdi, The Internet and the New Biology: Tools for Genomicand Molecular Research (ASM Press, Inc. 1997); Wu et al. (eds.),“Information Superhighway and Computer Databases of Nucleic Acids andProteins,” in Methods in Gene Biotechnology 123-151 (CRC Press, Inc.1997); Bishop (ed.), Guide to Human Genome Computing (2nd ed., AcademicPress, Inc. 1998).) Two nucleotide or amino acid sequences areconsidered to have “substantially similar sequence identity” or“substantial sequence identity” if the two sequences have at least 80%,at least 90%, or at least 95% sequence identity relative to each other.

Percent sequence identity is determined by conventional methods. See,e.g., Altschul et al., Bull. Math. Bio. 48:603, 1986, and Henikoff andHenikoff, Proc. Natl. Acad. Sci. USA 89:10915, 1992. For example, twoamino acid sequences can be aligned to optimize the alignment scoresusing a gap opening penalty of 10, a gap extension penalty of 1, and the“BLOSUM62” scoring matrix of Henikoff and Henikoff, supra, as shown inTable 1 (amino acids are indicated by the standard one-letter codes).The percent identity is then calculated as: ([Total number of identicalmatches]/[length of the longer sequence plus the number of gapsintroduced into the longer sequence in order to align the twosequences])(100).

TABLE 1 BLOSUM62 Scoring Matrix A R N D C Q E G H I L K M F P S T W Y VA 4 R −1 5 N −2 0 6 D −2 −2 1 6 C 0 −3 −3 −3 9 Q −1 1 0 0 −3 5 E −1 0 02 −4 2 5 G 0 −2 0 −1 −3 −2 −2 6 H −2 0 1 −1 −3 0 0 −2 8 I −1 −3 −3 −3 −1−3 −3 −4 −3 4 L −1 −2 −3 −4 −1 −2 −3 −4 −3 2 4 K −1 2 0 −1 −3 1 1 −2 −1−3 −2 5 M −1 −1 −2 −3 −1 0 −2 −3 −2 1 2 −1 5 F −2 −3 −3 −3 −2 −3 −3 −3−1 0 0 −3 0 6 P −1 −2 −2 −1 −3 −1 −1 −2 −2 −3 −3 −1 −2 −4 7 S 1 −1 1 0−1 0 0 0 −1 −2 −2 0 −1 −2 −1 4 T 0 −1 0 −1 −1 −1 −1 −2 −2 −1 −1 −1 −1 −2−1 1 5 W −3 −3 −4 −4 −2 −2 −3 −2 −2 −3 −2 −3 −1 1 −4 −3 −2 11 Y −2 −2 −2−3 −2 −1 −2 −3 2 −1 −1 −2 −1 3 −3 −2 −2 2 7 V 0 −3 −3 −3 −1 −2 −2 −3 −33 1 −2 1 −1 −2 −2 0 −3 −1 4

Those skilled in the art appreciate that there are many establishedalgorithms available to align two amino acid sequences. The “FASTA”similarity search algorithm of Pearson and Lipman is a suitable proteinalignment method for examining the level of identity shared by an aminoacid sequence disclosed herein and a second amino acid sequence. TheFASTA algorithm is described by Pearson and Lipman, Proc. Nat'l Acad.Sci. USA 85:2444, 1988, and by Pearson, Meth. Enzymol. 183:63, 1990.Briefly, FASTA first characterizes sequence similarity by identifyingregions shared by the query sequence (e.g., residues 39-301 of SEQ IDNO:40, residues 48-310 of SEQ ID NO:42, residues 24-286 of SEQ ID NO:44,or residues 24-286 of SEQ ID NO:46) and a test sequence that have eitherthe highest density of identities (if the ktup variable is 1) or pairsof identities (if ktup-2), without considering conservative amino acidsubstitutions, insertions, or deletions. The ten regions with thehighest density of identities are then rescored by comparing thesimilarity of all paired amino acids using an amino acid substitutionmatrix, and the ends of the regions are “trimmed” to include only thoseresidues that contribute to the highest score. If there are severalregions with scores greater than the “cutoff” value (calculated by apredetermined formula based upon the length of the sequence and the ktupvalue), then the trimmed initial regions are examined to determinewhether the regions can be joined to form an approximate alignment withgaps. Finally, the highest scoring regions of the two amino acidsequences are aligned using a modification of theNeedleman-Wunsch-Sellers algorithm (Needleman and Wunsch, J. Mol. Biol.48:444, 1970; Sellers, SIAM J. Appl. Math. 26:787, 1974), which allowsfor amino acid insertions and deletions. Illustrative parameters forFASTA analysis are: ktup=1, gap opening penalty=10, gap extensionpenalty=1, and substitution matrix=BLOSUM62. These parameters can beintroduced into a FASTA program by modifying the scoring matrix file(“SMATRIX”), as explained in Appendix 2 of Pearson, Meth. Enzymol.183:63, 1990.

FASTA can also be used to determine the sequence identity of nucleicacid molecules using a ratio as disclosed above. For nucleotide sequencecomparisons, the ktup value can range between one to six, preferablyfrom three to six, most preferably three, with other parameters set asdescribed above.

“Conservative amino acid substitution” generally refers to an amino acidsubstitution represented by a BLOSUM62 value of greater than −1. TheBLOSUM62 table (Table 1, supra) is an amino acid substitution matrixderived from about 2,000 local multiple alignments of protein sequencesegments, representing highly conserved regions of more than 500 groupsof related proteins (Henikoff and Henikoff, Proc. Nat'l Acad. Sci. USA89:10915, 1992). Accordingly, the BLOSUM62 substitution frequencies canbe used to define conservative amino acid substitutions that may beintroduced into a particular amino acid sequence. For example, an aminoacid substitution is conservative if the substitution is characterizedby a BLOSUM62 value of 0, 1, 2, or 3. According to this system,preferred conservative amino acid substitutions are characterized by aBLOSUM62 value of at least 1 (e.g., 1, 2 or 3), while more preferredconservative amino acid substitutions are characterized by a BLOSUM62value of at least 2 (e.g., 2 or 3).

“Corresponding to,” when used in reference to a nucleotide or amino acidsequence, indicates the position in a second sequence that aligns withthe reference position when two sequences are optimally aligned.

With regard to FcγR polypeptides as described herein, reference to aminoacid residues corresponding to those specified by SEQ ID NO includespost-translational modifications of such residues. For example,reference to a glutamine at a position corresponding to position 16 ofSEQ ID NO:2 encompasses a post-translational modification of thisglutamine to pyro-glutamic acid.

“Immune complex,” as used herein, refers to a complex that forms uponbinding of an IgG antibody to its cognate antigen. The term “immunecomplex” as used herein encompasses all stoichiometries ofantigen:antibody complexes. For example, an immune complex may comprisea single IgG antibody (monomeric IgG) bound to antigen or may comprisemultiple IgG antibodies bound to antigen (multimeric immune complex).

“IgG-mediated inflammation,” as used herein, refers to an inflammatoryresponse mediated at least in part by the binding of an immune complexto an Fcγ receptor via the Fc region of an IgG antibody contained withinthe immune complex. “IgG-mediated inflammation” also encompasses theactivation of the complement pathway by IgG immune complexes.

“Immune complex-mediated inflammation,” as used herein, refers toIgG-mediated inflammation characterized at least in part by thedeposition of immune complexes within one or more tissues.

“IgG-mediated disease” or “IgG-mediated inflammatory disease,” as usedherein, refers to an inflammatory disease mediated at least in part bythe binding of an immune complex to an Fcγ receptor via the Fc region ofan IgG antibody contained within the immune complex. “IgG-mediateddisease” or “IgG-mediated inflammatory disease” also encompassesdiseases characterized at least in part by the activation of thecomplement pathway by IgG immune complexes.

“Autoimmune disease,” as used herein, refers to an IgG-mediatedinflammatory disease characterized at least in part by the presence ofIgG autoantibodies, i.e., IgG antibodies specific for one or moreself-antigens. Autoimmune diseases include, for example, diseasesassociated with autoantibody production as well as the deposition ofimmune complexes in one or more tissues; such diseases include, e.g.,systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and mixedconnective tissue disease. Autoimmune diseases also include thosediseases associated with autoantibody production although not clearlyassociated with deposition of immune complexes, such as, for example,idiopathic thrombocytopenia purpura (ITP), Sjogren's Syndrome,antiphospholipid antibody syndrome, dermatomyositis, Guillain-BarreSyndrome, and Goodpasture's Syndrome. Other autoimmune diseases include,e.g., inflammatory bowel disease (IBD), psoriasis, atopic dermatitis,myasthenia gravis, type I diabetes, and multiple sclerosis.

“Immune complex-mediated disease,” as used herein, refers to anIgG-mediated inflammatory disease characterized at least in part by thedeposition of immune complexes within one or more tissues. Immunecomplex-mediated diseases include, for example, mixed cryoglobulinemia;systemic lupus erythematosus (SLE); rheumatoid arthritis (RA); mixedconnective tissue disease; and diseases associated with exonegousantigens such as, e.g., HBV-associated polyarteritis nodosa.

Due to the imprecision of standard analytical methods, molecular weightsand lengths of polymers are understood to be approximate values. Whensuch a value is expressed as “about” X or “approximately” X, the statedvalue of X will be understood to be accurate to 110%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts blocking of immune complex precipitation in vitro withFcγRIA-CH6. Anti-OVA/OVA immune complex precipitation assays werecarried out as described in Example 9, infra. Each point represents themean values of three separate experiments performed in duplicate.Circles: anti-OVA+OVA; triangles: anti-OVA+OVA+500 nM FcγRIA-CH6;squares: anti-OVA+OVA+1500 nM FcγRIA-CH6.

FIGS. 2A-2D depict inhibition of immune complex-mediated production ofinflammatory cytokines in mast cells with FcγRIA-CH6. Murine MC/9 mastcells were incubated with anti-OVA/OVA immune complexes in the presenceof increasing amounts of FcγRIA-CH6 (“pFCGR1A CH6”) and secretion ofinflammatory cytokines were determined as described in Example 9, infra.Each point represents the mean value of duplicate determinations and isrepresentative of two separate experiments.

FIGS. 3A-3C depict inhibition of immune complex-mediated edema andneutrophil infiltration in the murine Arthus reaction with FcγRIA-CH6.The cutaneous reversed passive Arthus reaction was established in miceusing intradermal delivery of rabbit anti-ovalbumin and tail veininjection of ovalbumin. (See Example 9, infra.) Animals received eitheranti-OVA alone or anti-OVA together with the indicated amount ofFcγRIA-CH6 (“pFCGRIA CH6”), and the effects of FcγRIA-CH6 on immunecomplex-mediated edema and neutrophil infiltration were assessed. (Seeid.) Each bar represents the mean±SD for n=8 animals per group. 0.1×,1.0×, and 7.0×pFCGRIA-CH6 represents the molar excess of FcγRIA-CH6added relative to the amount of anti-OVA injected and is equivalent to1.3 μg, 13.0 μg, and 91.0 μg of with FcγRIA-CH6, respectively.

FIG. 4 depicts inhibition of inflammation in the Arthus reaction in micewith systemic delivery of FcγRIA-CH6. Mice were injected with theindicated amounts of either vehicle alone or vehicle containing theindicated amount of FcγRIA-CH6 (“pFCGRIA CH6”) 1 hour prior toinitiating the Arthus reaction. (See Example 9, infra.) Systemicadministration of FcγRIA-CH6 was performed by intravenous injection, andthe cutaneous reversed passive Arthus reaction was carried out usingintradermal delivery of rabbit anti-ovalbumin, as described in Example9. Edema was measured by anti-OVA induced extravasation of Evan's Bluedye. Each bar represents the mean±SD for n=8 mice (intravenous injectionof FcγRIA-CH6) or n=4 mice (intradermal injection of FcγRIA-CH6). Theabbreviations used are: iv=intravenous; id=intradermal.

FIG. 5 depicts inhibition of edema in the Arthus reaction in mice withsystemic delivery of FcγRIA-CH6. Mice were injected with the indicatedamounts of either vehicle alone or vehicle containing the indicatedamount of FcγRIA-CH6 (“pFCGRIA CH6”) 1 hour prior to initiating theArthus reaction. (See Example 9, infra.) Systemic administration ofFcγRIA-CH6 was performed by intravenous injection, and the cutaneousreversed passive Arthus reaction was carried out using intradermaldelivery of rabbit anti-ovalbumin, as described in Example 9. Edema wasmeasured by anti-OVA induced increases in tissue weights of the lesionsites. Each bar represents the mean±SD for n=8 mice (intravenousinjection of FcγRIA-CH6) or n=4 mice (intradermal injection ofFcγRIA-CH6). The data are expressed relative to injection of nonimmuneIgG. The abbreviations used are: iv=intravenous; id=intradermal.

FIGS. 6A-6D depict FcγRI sequences. FIG. 6A shows a polynucleotidesequence encoding FcγRIA (FcγRI isoform a) (SEQ ID NO:1). FIG. 6B showsthe polypeptide sequence of FcγRIA (SEQ ID NO:2). FIG. 6C shows thepolypeptide sequence of the extracellular domain of FcγRIA (SEQ IDNO:3). FIG. 6D shows a comparison of FcγRIA polypeptide sequence withFcγRI isoforms b1 (SEQ ID NO:4) and c (SEQ ID NO:5) polypeptidesequences. The vertical lines in FIG. 6D indicate where the introns arelocated in the corresponding gene; the triangle indicates the C-terminalamino acid of a particular embodiment of soluble FcγRIA or,alternatively, a C-terminal fusion site for certain tagged variations ofsoluble FcγRIA (e.g., His6-tagged FcγRIA). “16” above glutamine (Q) atamino acid position 16 in FIG. 6D indicates the amino terminal startsite for the mature FcγRIA protein.

FIG. 7 depicts reduction of paw scores in the collagen antibody-inducedarthritis mouse model with Fc RIA-CH6. Collagen antibody-inducedarthritis was established in mice by treatment with the Arthrogen-CIA®antibody cocktail, as described in Example 11, infra. Mice also receivedeither sub-cutaneous injections of either vehicle alone (PBS) or vehiclecontaining the indicated concentration of FcγRIA-CH6 (“pFCGRIA CH6”),every other day for a total of five doses. Each point represents themean±SEM for n=8 mice per group. Differences between groups weresignificant by repeated measures ANOVA.

FIG. 8 depicts reduction of paw thickness in the collagenantibody-induced arthritis mouse model with FcγRIA-CH6. Collagenantibody-induced arthritis was established in mice by treatment with theArthrogen-CIA® antibody cocktail, as described in Example 11, infra.Mice also received either sub-cutaneous injections of either vehiclealone (PBS) or vehicle containing the indicated concentration ofFcγRIA-CH6 (“pFCGRIA CH6”), every other day for a total of five doses.Each point represents the mean±SEM for n=8 mice per group. Differencesbetween groups were significant by repeated measures ANOVA.

FIGS. 9A-9C depict reduction in inflammation in the Arthus reaction byFcγRIA-CH6 but by neither FcγRIIA-CH6 nor FcγRIIIA-CH6. Experiments werecarried out as described in Examples 9 and 10, infra. The data areexpressed relative to that observed in the presence of anti-OVA aloneafter subtracting the values for non-immune IgG from each point. Eachpoint, FcγRIA (●), FcγRIIA (▴), FcγRIIIA (▪), represents the mean±SEMfor n=8-16 lesion sites (FIGS. 9A and 9B) and for n=5-13 lesion sites(FIG. 9C) from six separate experiments. Differences were significant,*p<0.0001 across all dose groups by ANOVA.

FIG. 10 depicts reduction in arthritis disease scores by treatment withFcγRIA. Collagen-induced arthritis (CIA) was established in mice asdescribed in Example 13, infra. Once established disease was present,mice were treated with vehicle alone (PBS) (◯), or vehicle containing0.22 mg or 2.0 mg FcγRIA (“FCGR1A”). (See Example 13, infra.) Each pointrepresents the mean±SE for 7-13 animals per group. Differences weresignificant, *p=0.001 by repeated measures ANOVA.

FIG. 11 depicts reduction in arthritis scores with an extended FcγRIAdose regimen. Collagen-induced arthritis (CIA) was established in miceas described in Example 13, infra. Mice were treated with vehicle alone(◯) or vehicle containing 2.0 mg FcγRIA dosed either every other day (▪)or every fourth day (▴). (See Example 13, infra.) Each point representsthe mean±SE for 7-13 animals per group. Differences were significant,*p=0.0125, **p=0.001 by repeated measures ANOVA. Every fourth day dosingwas for 11 days total.

FIG. 12 depicts reduction in the number of arthritic paws with FcγRIAtreatment. Collagen-induced arthritis (CIA) was established in mice asdescribed in Example 13, infra. Mice were treated every other day withvehicle alone (◯) or vehicle containing 0.22 mg FcγRIA (▾) or 2.0 mg (▪)of FcγRIA dosed either every other day. (See Example 13, infra.) Eachpoint represents the mean of 7-13 mice per group.

FIGS. 13A-13D depict inhibition of immune complex-mediated cytokineproduction in cultured mast cells by incubation with soluble nativeFcγRIA and soluble hybrid FcγRIIA/IA and FcγRIIIA/IA receptors. MurineMC/9 mast cells were incubated with anti-OVA/OVA immune complexes in thepresence of increasing amounts of soluble native FcγRIA (“NativeFCGR1A”), or one of two soluble hybrid receptors, FcγRIIA/IA-CH6(“FCGR2A1A”) or FcγRIIIA/IA-CH6 (“FCGR3A1A”) and secretion ofinflammatory cytokines, IL-6 (FIG. 13A), IL-13 (FIG. 13B), TNFα (FIG.13C), and MCP-1 (FIG. 13D), were determined as described in Example 22,infra.

FIGS. 14A and 14B depict inhibition of immune complex-mediated edema inthe murine Arthus reaction with soluble native FcγRIA and the solublehybrid receptor, FcγRIIA/IA. The cutaneous reversed passive Arthusreaction was established in mice using intradermal delivery of rabbitanti-ovalbumin and tail vein injection of ovalbumin. (See Example 22,infra.) Animals received either anti-OVA alone or anti-OVA together withthe indicated amount of soluble native FcγRIA (“Native FCGR1A”), or thesoluble hybrid receptor, FcγRIIA/IA-CH6 (“FCGR2A1A”), and the effects ofeach soluble receptor on immune complex-mediated edema were assessed bymeasuring either a decrease in Evan's blue area (FIG. 14A) or a decreasein tissue weight of the lesion site (FIG. 14B). (See id.) Each pointrepresents the mean±SD for n=6 animals per group. Differencessignificant relative to anti-OVA alone, *p<0.001 by ANOVA.

FIGS. 15A and 15B depict inhibition of immune complex-mediated edema inthe cutaneous Arthus reaction in mice with soluble native FcγRIA and thesoluble hybrid receptor, FcγRIIIA/IA. The cutaneous reversed passiveArthus reaction was established in mice using intradermal delivery ofrabbit anti-ovalbumin and tail vein injection of ovalbumin. (See Example22, infra.) Animals received either anti-OVA alone or anti-OVA togetherwith the indicated amount of soluble native FcγRIA (“Native FCGR1A”), orthe soluble hybrid receptor, FcγRIIIA/IA-CH6 (“FCGR3A1A”), and theeffects of each soluble receptor on immune complex-mediated edema wereassessed by measuring either a decrease in Evan's blue area (FIG. 15A)or a decrease in tissue weight of the lesion site (FIG. 15B). (See id.)Each point represents the mean±SD for n=6 animals per group. Differencesignificant, *p<0.001 by ANOVA.

FIGS. 16A and 16B depict inhibition of neutrophil infiltration in thecutaneous Arthus reaction in mice with soluble native FcγRIA and thesoluble hybrid receptors, FcγRIIA/IA-CH6 and FcγRIIIA/IA-CH6. Thecutaneous reversed passive Arthus reaction was established in mice usingintradermal delivery of rabbit anti-ovalbumin and tail vein injection ofovalbumin. (See Example 22, infra.) Animals received either anti-OVAalone or anti-OVA together with the indicated amount of soluble nativeFcγRIA (“FCGR1A”; FIGS. 16A and 16B), or one of the soluble hybridreceptors, FcγRIIA/IA-CH6 (“FCGR2A 1A”; FIG. 16A) and FcγRIIIA/IA-CH6(“FCGR3A IA”; FIG. 16B), and neutrophil infiltration was assessed bymeasuring myeloperoxidase activity in the punch biopsy samples. Eachpoint represents the mean±SD for n=6 animals per group. Differencesignificant, *p<0.001 by ANOVA, **p<0.001 by the Mann-Whitney test.

DESCRIPTION OF THE INVENTION I. Overview

The present invention fills a need for novel therapeutics for treatingIgG- and immune complex-mediated disease by providing Fcγ receptorantagonists. In particular, Fcγ receptor antagonists in accordance withthe present invention are soluble hybrid receptors comprising a modifiedextracellular domain of FcγRIA in which the first Ig domain (D1) issubstituted with the first Ig domain of FcγRIIA, FcγRIIB, FcγRIIA, orFcγRIIIB. Such hybrid receptors maintain the high affinity binding ofthe native FcγRIA and may be used in methods for reducing IgG-mediatedinflammation, including inflammatory processes mediated by immunecomplex precipitation.

It was discovered that soluble FcγRIA, but not soluble FcγRIIA orFcγRIIA, blocked inflammation in the cutaneous Arthus reaction (seeExamples 9 and 10). Additionally, it was discovered that soluble FcγRIAalso blocked the binding and signaling of immune complexes (described indetail in the Examples below) through cellular FcγR. The findings thatsoluble FcγRIA blocked inflammation in the cutaneous Arthus reaction, inthe collagen antibody-induced model of arthritis, and incollagen-induced arthritis in mice were surprising, since FcγRIA, as ahigh affinity receptor for IgG Fc, is expected to be saturated withmonomeric IgG in the circulation and hence generally less available forbinding to immune complexes. These findings show that soluble FcγRIA isa potent therapeutic that can be used to treat autoimmune disease andinflammation. Further, these results support the use of other soluble,high-affinity receptors for Fcγ, including the hybrid Fcγ receptors asdescribed herein, for treating such conditions.

Accordingly, the soluble Fcγ receptor polypeptides described herein areuseful to antagonize or block signaling of IgG and immune complexes inimmune cells (e.g., lymphocytes, monocytes, leukocytes, macrohages andNK cells) for the treatment of IgG- and immune complex-mediated diseasessuch as, for example, autoimmune diabetes, multiple sclerosis (MS),systemic Lupus erythematosus (SLE), myasthenia gravis, Wegener'sgranulomatosis, Churg-Strauss syndrome, hepatitis-B-associatedpolyarteritis nodosa, microscopic polyangiitis, Henoch-Schonleinpurpura, rheumatoid arthritis (RA), Lambert-Eaton syndrome, inflammatorybowel disease (IBD), essential mixed cryoglobulinemia,hepatitis-C-associated cryoglobulinemia, mixed connective tissuedisease, autoimmune thrombocytopenias (ITP and TTP), adultdermatomyositis, Guillian-Barre syndrome, Sjogren's syndrome,Goodpasture's syndrome, chronic inflammatory demyelinatingpolyneuropathies, anti-phospholipid antibody syndrome, vasculitis,uveitis, serum sickness, pemphigus (e.g., pemphigus vulgaris), anddiseases associated with exogenous antigens, such as viral and bacterialinfections. Asthma, allergy, and other atopic disease may also betreated with the soluble Fey receptor polypeptides of the invention toinhibit the immune response or to deplete offending cells. Blocking orinhibiting signaling of IgG and immune complexes via Fcγ receptors, byusing the soluble Fey receptor polypeptides of the present invention,may also benefit diseases of the pancreas, kidney, pituitary, andneuronal cells. The soluble Fcγ receptor polypeptides of the presentinvention are useful as antagonists of IgG and immune complexes. Suchantagonistic effects can be achieved by direct neutralization or bindingof the Fc domains IgG and immune complexes.

II. Soluble Hybrid Fcγ Receptors and Methods and Materials for MakingThem

Accordingly, in one aspect, the present invention provides isolated,soluble hybrid Fcγ receptor (FcγR) polypeptides capable of neutralizingIgG- or immune-complex-mediated signaling in immune cells. The hybridFcγ receptors generally comprise polypeptide regions corresponding tothe extracellular Ig domains of at least two different Fcγ receptorsubfamilies and are substantially free of transmembrane andintracellular polypeptide segments. In particular, a soluble hybrid Fcγreceptor of the present invention generally comprises a modifiedextracellular domain of human FcγRIA in which the first Ig domain (D1)is substituted with a polypeptide region corresponding to the first Igdomain of human FcγRIIA, FcγRIIB, FcγRIIIA, or FcγRIIIB.

An illustrative nucleotide sequence that encodes human FcγRIA (isoform aof FcγRI) is provided by SEQ ID NO:1 SEQ ID NO:1 contains an openreading frame encoding 374 amino acids (SEQ ID NO:2) comprising anextracellular Fcγ-binding domain of approximately 277 amino acidresidues (residues 16-292 of SEQ ID NO:2; SEQ ID NO:3). FcγRI alsoincludes isoforms b1 and c, both of which are depicted in FIG. 6D ascompared to FcγRIA (SEQ ID NO:2). The extracellular domain of isoformsb1 and c comprise only two Ig domains, as opposed to that of isoform a,which comprises three Ig domains. The first, second, and third Igdomains of FcγRIA correspond approximately to amino acid residues22-101, 104-184, and 190-250 of SEQ ID NO:2, respectively.

An illustrative nucleotide sequence that encodes an extracellular domainof human FcγRIIA (isoform a of FcγRII) is provided by SEQ ID NO:6. SEQID NO:6 contains an open reading frame encoding 211 amino acids (SEQ IDNO:7) comprising a secretory signal sequence of approximately 34 or 35amino acid residues (residues 1-34 or 1-35 of SEQ ID NO:7) and anextracellular Fcγ-binding domain of approximately 177 or 176 amino acidresidues (residues 35-211 or 36-211 of SEQ ID NO:7). The extracellulardomain of FcγRIIA comprises two Ig domains, corresponding approximatelyto amino acid residues 39-119 and 122-204 of SEQ ID NO:7, respectively.

An illustrative nucleotide sequence that encodes an extracellular domainof human FcγRIIB (isoform b of FcγRII) is provided by SEQ ID NO:8. SEQID NO:8 contains an open reading frame encoding 216 amino acids (SEQ IDNO:9) comprising a secretory signal sequence of approximately 42 aminoacid residues (residues 1-42 of SEQ ID NO:9) and an extracellularFcγ-binding domain of approximately 174 amino acid residues (residues43-216 of SEQ ID NO:9). The extracellular domain of FcγRIIB comprisestwo Ig domains, corresponding approximately to amino acid residues48-129 and 132-213 of SEQ ID NO:9, respectively.

An illustrative nucleotide sequence that encodes an extracellular domainof human FcγRIIIA (isoform a of FcγRIII) is provided by SEQ ID NO:10.SEQ ID NO:10 contains an open reading frame encoding 195 amino acids(SEQ ID NO: 11) comprising a secretory signal sequence of approximately17 or 20 amino acid residues (residues 1-17 or 1-20 of SEQ ID NO:11) andan extracellular Fcγ-binding domain of approximately 178 or 175 aminoacid residues (residues 18-195 or 21-195 of SEQ ID NO:11). Theextracellular domain of FcγRIIIA comprises two Ig domains, correspondingapproximately to amino acid residues 24-105 and 108-189 of SEQ ID NO:11,respectively.

An illustrative nucleotide sequence that encodes an extracellular domainof human FcγRIIIB (isoform b of FcγRIII) is provided by SEQ ID NO:12.SEQ ID NO:12 contains an open reading frame encoding 195 amino acids(SEQ ID NO:13) comprising a secretory signal sequence of approximately17 or 20 amino acid residues (residues 1-17 or 1-20 of SEQ ID NO:13) andan extracellular Fcγ-binding domain of approximately 178 or 175 aminoacid residues (residues 18-195 or 21-195 of SEQ ID NO:13). Theextracellular domaino of FcγRIIIB comprises two Ig domains,corresponding approximately to amino acid residues 24-105 and 108-189 ofSEQ ID NO:13, respectively.

In certain embodiments, a soluble FcγR polypeptide of the inventioncomprises an amino acid sequence that is at least 70%, at least 80%, atleast 90%, at least 95%, at least 96%, at least 97%, at least 98%, or atleast 99% or more identical to amino acid residues 35-301, 36-301, or39-301 of SEQ ID NO:40; amino acid residues 43-310 or 48-310 of SEQ IDNO:42; amino acid residues 18-286, 21-286, or 24-286 of SEQ ID NO:44; oramino acid residues 18-286, 21-286, or 24-286 of SEQ ID NO:46, whereinthe isolated polypeptide is capable of specifically binding to the Fcdomain of IgG (e.g., human IgG such as, for example, human IgG1). Asoluble FcγR polypeptide of the invention specifically binds if it bindsto monomeric human IgG (e.g., human IgG1) with a binding affinity(K_(a)) of at least 10⁶ M⁻¹, preferably at least 10⁷ M⁻¹, morepreferably at least 10⁸ M⁻¹, and most preferably at least 10⁹ M⁻¹. Incertain embodiments, a soluble FcγR polypeptide of the invention bindsto monomeric human IgG with a binding affinity (K_(a)) of between 10⁸M⁻¹ and 10⁹ M⁻¹. The binding affinity of a soluble FcγR polypeptide canbe readily determined by one of ordinary skill in the art, for example,by Scatchard analysis (Scatchard, Ann. NY Acad. Sci. 51:660, 1949). Inaddition to determining an affinity constant (K_(a)), an alternativemeans of measuring affinity is the equilibrium constant (K_(d)), where adecrease would be observed with the improvement in affinity. In certainembodiments, a soluble FcγR polypeptide of the invention binds to humanIgG1 with an equilibrium dissociation constant (K_(d)) of less than 10⁻⁸M, preferably less than 10⁻⁹ M, and more preferably less than 10⁻¹⁰ M.In a specific variation, a soluble FcγR polypeptide of the inventionbinds to human IgG1 with an equilibrium dissociation constant (K_(d)) ofabout 1.7×10⁻¹⁰ M. In some embodiments, a soluble FcγR polypeptide ofthe invention comprises amino acid residues 35-301, 36-301, or 39-301 ofSEQ ID NO:40; amino acid residues 43-310 or 48-310 of SEQ ID NO:42;amino acid residues 18-286, 21-286, or 24-286 of SEQ ID NO:44; or aminoacid residues 18-286, 21-286, or 24-286 of SEQ ID NO:46. In otherembodiments, a soluble FcγR polypeptide of the invention comprises anamino acid sequence selected from (i) an amino acid sequence as shown inSEQ ID NO:40 from amino acid x to amino acid 301, wherein x is aninteger from 35 to 39, inclusive; (ii) an amino acid sequence as shownin SEQ ID NO:42 from amino acid x to amino acid 310, wherein x is aninteger from 43 to 48, inclusive; (iii) an amino acid sequence as shownin SEQ ID NO:44 from amino acid x to amino acid 286, wherein x is aninteger from 18 to 24, inclusive; and (iv) an amino acid sequence asshown in SEQ ID NO:46 from amino acid x to amino acid 286, wherein x isan integer from 18 to 24, inclusive.

In some embodiments in which the amino acid sequence of the solublehybrid FcγRI polypeptide shares at least 70%, at least 80%, at least90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least99% or more identity with amino acid residues 35-301, 36-301, or 39-301SEQ ID NO:40; amino acid residues 43-310 or 48-310 of SEQ ID NO:42;amino acid residues 18-286, 21-286, or 24-286 of SEQ ID NO:44; or aminoacid residues 18-286, 21-286, or 24-286 of SEQ ID NO:46, any differencebetween the amino acid sequence of the FcγR polypeptide and thecorresponding amino acid sequence of SEQ ID NO:40, SEQ ID NO:42, SEQ IDNO:44, or SEQ ID NO:46 is due to one or more conservative amino acidsubstitutions.

Polypeptides having substantial sequence identity relative to areference polypeptide as shown in SEQ ID NO:40, 42, 44, or 46 aregenerally characterized as having one or more amino acid substitutions,deletions or additions relative to the reference polypeptide. Thesechanges are preferably of a minor nature, that is conservative aminoacid substitutions (see, e.g., Table 2, infra, which lists someexemplary conservative amino acid substitutions) and other substitutionsthat do not significantly affect the folding or activity of the proteinor polypeptide; small deletions, typically of one to about 30 aminoacids; and small amino- or carboxyl-terminal extensions, such as anamino-terminal methionine residue, a small linker peptide of up to about20-25 residues, or a small extension that facilitates purification (anaffinity tag), such as a poly-histidine tract, protein A (Nilsson etal., EMBO J. 4:1075, 1985; Nilsson et al., Methods Enzymol. 198:3,1991), glutathione S transferase (Smith and Johnson, Gene 67:31, 1988),or other antigenic epitope or binding domain. (See generally Ford etal., Protein Expression and Purification 2:95-107, 1991.) DNAs encodingaffinity tags are available from commercial suppliers (e.g., PharmaciaBiotech, Piscataway, N.J.).

TABLE 2 Conservative amino acid substitutions Basic: arginine lysinehistidine Acidic: glutamic acid aspartic acid Polar: glutamineasparagine Hydrophobic: leucine isoleucine valine Aromatic:phenylalanine tryptophan tyrosine Small: glycine alanine serinethreonine methionine

Essential amino acids in the receptor polypeptides of the presentinvention can be identified according to procedures known in the art,such as site-directed mutagenesis or alanine-scanning mutagenesis(Cunningham and Wells, Science 244:1081-1085, 1989; Bass et al., Proc.Natl. Acad. Sci. USA 88:4498-4502, 1991). In the latter technique,single alanine mutations are introduced at every residue in themolecule, and the resultant mutant molecules are tested for biologicalactivity (e.g., ligand binding and signal transduction) to identifyamino acid residues that are critical to the activity of the molecule.Sites of ligand-receptor interaction can also be determined by analysisof crystal structure as determined by such techniques as nuclearmagnetic resonance, crystallography or photoaffinity labeling. (See,e.g., de Vos et al., Science 255:306-312, 1992; Smith et al., J. Mol.Biol. 224:899-904, 1992; Wlodaver et al., FEBS Lett. 309:59-64, 1992.)The identities of essential amino acids can also be inferred fromanalysis of homologies with related receptors.

Multiple amino acid substitutions can be made and tested using knownmethods of mutagenesis and screening, such as those disclosed byReidhaar-Olson and Sauer Science 241:53-57, 1988 or Bowie and SauerProc. Natl. Acad. Sci. USA 86:2152-2156, 1989. Briefly, these authorsdisclose methods for simultaneously randomizing two or more positions ina polypeptide, selecting for functional polypeptide, and then sequencingthe mutagenized polypeptides to determine the spectrum of allowablesubstitutions at each position. Other methods that can be used includephage display e.g., Lowman et al., Biochem. 30:10832-10837, 1991; Ladneret al., U.S. Pat. No. 5,223,409; Huse, WIPO Publication WO 92/06204) andregion-directed mutagenesis (Derbyshire et al., Gene 46:145, 1986; Neret al., DNA 7:127, 1988).

Mutagenesis methods as disclosed above can be combined withhigh-throughput screening methods to detect activity of cloned,mutagenized receptors in host cells. Preferred assays in this regardinclude cell proliferation assays and biosensor-based ligand-bindingassays, which are described below. Mutagenized DNA molecules that encodeactive receptors or portions thereof (e.g., ligand-binding fragments)can be recovered from the host cells and rapidly sequenced using modernequipment. These methods allow the rapid determination of the importanceof individual amino acid residues in a polypeptide of interest, and canbe applied to polypeptides of unknown structure.

Using the methods discussed above, one of ordinary skill in the art canprepare a variety of polypeptides that comprise a soluble FcγRpolypeptide that is substantially identical to a reference polypeptideof amino acid residues 35-301, 36-301, or 39-301 of SEQ ID NO:40; aminoacid residues 43-310 or 48-310 of SEQ ID NO:42; amino acid residues18-286, 21-286, or 24-286 of SEQ ID NO:44; or amino acid residues18-286, 21-286, or 24-286 of SEQ ID NO:46 and that retains theligand-binding properties (i.e. IgG binding properties) of the referencepolypeptide. Assay systems for determining ligand-binding properties ofreceptor polypeptides are generally known in the art and are readilyadaptable for use in determining the Fcγ-binding properties of a solublehybrid FcγR as described herein. Exemplary assays are further describedherein.

For example, a preferred assay system employs a commercially availablebiosensor instrument (BIAcore™, Pharmacia Biosensor, Piscataway, N.J.),wherein a receptor polypeptide is immobilized onto the surface of areceptor chip. Use of this instrument is disclosed by Karlsson (J.Immunol. Methods 145:229-240, 1991) and Cunningham and Wells (J. Mol.Biol. 234:554-563, 1993). For use in accordance with the presentinvention, a soluble hybrid FcγR polypeptide is covalently attached,using amine or sulfhydryl chemistry, to dextran fibers that are attachedto gold film within the flow cell. A test sample is passed through thecell. If ligand (e.g., IgG) is present in the sample, it will bind tothe immobilized hybrid FcγR, causing a change in the refractive index ofthe medium, which is detected as a change in surface plasmon resonanceof the gold film. This system allows the determination of on- andoff-rates, from which binding affinity can be calculated, and assessmentof stoichiometry of binding.

The soluble hybrid FcγR polypeptides can also be used within other assaysystems known in the art. Such systems include Scatchard analysis fordetermination of binding affinity (see Scatchard, Ann. NY Acad. Sci. 51:660-672, 1949) and calorimetric assays (see Cunningham et al., Science253:545-548, 1991; Cunningham et al., Science 254:821-825, 1991).

Soluble hybrid FcγR polypeptides in accordance with the presentinvention may also include one or more additional polypeptide segment(s)that are not derived from a native FcγR. Accordingly, in someembodiments, a soluble hybrid FcγR polypeptide is a fusion proteinfurther comprising a polypeptide segment heterologous to a Fcγ receptor.Particularly suitable heterologous polypeptides are dimerizing proteinsas disclosed, e.g., in U.S. Pat. Nos. 5,155,027 and 5,567,584. Preferreddimerizing proteins in this regard include immunoglobulin constantregion domains, e.g., IgGγ1, and the human κ light chain.Immunoglobulin-soluble FcγR polypeptide fusions can be expressed ingenetically engineered cells to produce a variety of such receptoranalogs. In certain variations, the dimerizing protein is animmunoglobulin heavy chain constant region, typically an Fc fragment,which contains two constant region domains and a hinge region but lacksthe variable region (See Sledziewski et al., U.S. Pat. Nos. 6,018,026and 5,750,375). Such fusions are typically secreted as multimericmolecules, wherein the dimerizing proteins are bonded to each other(e.g., via disulfide bonding) and two polypeptides are arrayed in closedproximity to each other.

Auxiliary domains can be fused to a soluble hybrid FcγR polypeptide totarget the polypeptide to specific cells, tissues, or macromolecules(e.g., collagen, or cells expressing other Fc receptors). In someembodiments, an affinity tag (e.g., maltose protein; an immunoglobulindomain; or a polyhistidine tag such as that shown, for example, in SEQID NO: 18) is fused to a soluble hybrid FcγR polypeptide to facilitatepurification. In some variations, a soluble hybrid FcγR polypeptide isfused to two or more moieties, such as an affinity tag for purificationand a targeting domain. Polypeptide fusions can also comprise one ormore cleavage sites, particularly between domains. See, e.g., Tuan etal., Connective Tissue Research 34:1-9, 1996.

The present invention also provides polynucleotide molecules, includingDNA and RNA molecules, that encode the soluble hybrid Fcγ receptorpolypeptides disclosed herein. The polynucleotides of the presentinvention include both single-stranded and double-stranded molecules.Illustrative DNA sequences encoding soluble hybrid Fcγ receptors aredisclosed herein. Additional DNA sequences encoding soluble hybrid Fcγreceptors of the present invention can be readily generated by those ofordinary skill in the art based on the genetic code. Counterpart RNAsequences can be generated by substitution of U for T. Those skilled inthe art will readily recognize that, in view of the degeneracy of thegenetic code, considerable sequence variation is possible amongpolynucleotide molecules encoding a given polypeptide.

Accordingly, in another aspect, the present invention provides anisolated polynucleotide that encodes a soluble hybrid FcγR polypeptideas described herein. Generally, an isolated polynucleotide of theinvention encodes a soluble FcγR polypeptide comprising an amino acidsequence that is at least 70%, at least 80%, at least 90%, at least 95%,at least 96%, at least 97%, at least 98%, or at least 99% or moreidentical to amino acid residues 35-301, 36-301, or 39-301 of SEQ IDNO:40; amino acid residues 43-310 or 48-310 of SEQ ID NO:42; amino acidresidues 18-286, 21-286, or 24-286 of SEQ ID NO:44; or amino acidresidues 18-286, 21-286, or 24-286 of SEQ ID NO:46, wherein the encodedpolypeptide is capable of specifically binding to the Fc domain of IgG(e.g., human IgG such as, for example, human IgG1). In some embodiments,the encoded polypeptide comprises amino acid residues 35-301, 36-301, or39-301 of SEQ ID NO:40; amino acid residues 43-310 or 48-310 of SEQ IDNO:42; amino acid residues 18-286, 21-286, or 24-286 of SEQ ID NO:44; oramino acid residues 18-286, 21-286, or 24-286 of SEQ ID NO:46. In otherembodiments, the encoded polypeptide comprises an amino acid sequenceselected from (i) an amino acid sequence as shown in SEQ ID NO:40 fromamino acid x to amino acid 301, wherein x is an integer from 35 to 39,inclusive; (ii) an amino acid sequence as shown in SEQ ID NO:42 fromamino acid x to amino acid 310, wherein x is an integer from 43 to 48,inclusive; (iii) an amino acid sequence as shown in SEQ ID NO:44 fromamino acid x to amino acid 286, wherein x is an integer from 18 to 24,inclusive; and (iv) an amino acid sequence as shown in SEQ ID NO:46 fromamino acid x to amino acid 286, wherein x is an integer from 18 to 24,inclusive. In specific variations, the nucleic acid comprises nucleotideresidues 103-903, 106-903, or 115-903 of SEQ ID NO:39; nucleotideresidues 127-930 or 142-930 of SEQ ID NO:41; nucleotide residues 52-858,61-858, or 70-858 of SEQ ID NO:43; or nucleotide residues 52-858,61-858, or 70-858 of SEQ ID NO:45.

The soluble hybrid Fcγ receptors and nucleic acids of the presentinvention are preferably recombinant (unless made synthetically).Recombinant DNA methods known in the art and may be readily used togenerate an FcγR polypeptide as described herein. As noted above, hybridreceptors in accordance with the present invention are derived from theextracellular domain of human FcγRIA, having the first Ig domain (D1)substituted with the first Ig domain of an Fcγ receptor of a differentsubclass (e.g., FcγRIIA, FcRIIA, FcγRIIA, or FcγRIIA). Accordingly,recombinant DNA methods may be used, for example, to clone particularnucleic acid segments encoding different polypeptide regions of a hybridreceptor (e.g., one nucleic acid segment encoding the second and thirdIg domains of FcγRIA and a second segment encoding the first Ig domainof FcγRIIA, FcγRIIA, FcγRIIA, or FcγRIIA), such as by PCR amplificationof the respective nucleic acid regions using RNA or DNA derived from asuitable tissue or cell expressing a native Fey receptor. Nucleic acidsegments encoding respective regions of a hybrid receptor may then bejoined using standard techniques such as, e.g., by ligation or overlapPCR.

DNA or RNA encoding one or more native Fcγ receptors, from which asoluble hybrid FcγR of the present invention may be derived, may beprepared according to methods well known in the art. Complementary DNA(cDNA) clones are prepared from RNA that is isolated from a tissue orcell that produces large amounts of RNA encoding a polypeptide ofinterest. Total RNA can be prepared using guanidine HCl extractionfollowed by isolation by centrifugation in a CsCl gradient (Chirgwin etal., Biochemistry 18:52-94, 1979). Poly (A)+ RNA is prepared from totalRNA using the method of Aviv and Leder (Proc. Natl. Acad. Sci. USA69:1408-1412, 1972). Complementary DNA is prepared from poly(A)+ RNAusing known methods. In the alternative, genomic DNA can be isolated.For some applications (e.g., expression in transgenic animals) it may beadvantageous to use a genomic clone, or to modify a cDNA clone toinclude at least one genomic intron. Methods for identifying andisolating cDNA and genomic clones are well known and within the level ofordinary skill in the art, and include the use of the sequencesdisclosed herein, or parts thereof, for probing or priming a library.Polynucleotides encoding polypeptides of interest are identified andisolated by, for example, hybridization or polymerase chain reaction(“PCR”, Mullis, U.S. Pat. No. 4,683,202). Expression libraries can beprobed with antibodies to the polypeptide of interest, receptorfragments, or other specific binding partners.

Variants of a specific hybrid Fcγ receptor may also be prepared usingknown techniques. Variants having one or more amino acid substitutions,deletions, or additions relative to a reference sequence may prepared,for example, by site-specific mutagenesis of nucleotides in the DNAencoding a corresponding hybrid Fcγ receptor protein, using cassette orPCR mutagenesis or another technique well known in the art, to produceDNA encoding the variant, and thereafter expressing the DNA inrecombinant cell culture. As outlined above, Fcγ receptor variants inaccordance with the present invention typically exhibit similar bindingof Fcγ relative to native FcγRIA, although variants can also be selectedthat have additional variant characteristics. Random mutagenesis may beconducted at a target codon or region and the expressed variant hybridFcγR protein screened for the optimal combination of desired activity.Techniques for making substitution mutations at predetermined sites inDNA having a known sequence are well-known, for example, M13 primermutagenesis and PCR mutagenesis.

Amino acid substitutions may be of single amino acid residues ormultiple amino acid residues (e.g., 2, 3, 4, or more amino acids can besubstituted). Insertions are typically on the order of from about 1 to20 about amino acids, although considerably larger insertions may betolerated. Deletions range from about 1 to about 20 residues, or fromabout 1 to about 30 residues, although in some cases deletions may bemuch larger. Substitutions, deletions, insertions, or any combinationthereof, are used to arrive at a final variant hybrid receptor. Incertain variations, modification(s) relative to a reference sequence aredone with respect to relatively few amino acids to minimize thealteration of the molecule. Larger changes, however, may be tolerated incertain circumstances.

The polynucleotides of the present invention can also be prepared byautomated synthesis. The production of short, double-stranded segments(60 to 80 bp) is technically straightforward and can be accomplished bysynthesizing the complementary strands and then annealing them. Longersegments (typically >300 bp) are assembled in modular form fromsingle-stranded fragments that are from 20 to 100 nucleotides in length.Automated synthesis of polynucleotides is within the level of ordinaryskill in the art, and suitable equipment and reagents are available fromcommercial suppliers. See generally Glick and Pasternak, MolecularBiotechnology, Principles & Applications of Recombinant DNA (ASM Press,Washington, D.C., 1994); Itakura et al., Ann. Rev. Biochem. 53: 323-356,1984; and Climie et al., Proc. Natl. Acad. Sci. USA 87:633-637, 1990.

The soluble hybrid Fey receptor polypeptides of the present inventioncan be produced in genetically engineered host cells according toconventional techniques. Suitable host cells are those cell types thatcan be transformed or transfected with exogenous DNA and grown inculture, and include bacteria, fungal cells, and cultured highereukaryotic cells (including cultured cells of multicellular organisms),particularly cultured mammalian cells. Techniques for manipulatingcloned DNA molecules and introducing exogenous DNA into a variety ofhost cells are disclosed by Sambrook et al., Molecular Cloning: ALaboratory Manual (2nd ed., Cold Spring Harbor Laboratory Press, ColdSpring Harbor, N.Y., 1989); and Ausubel et al., eds., Current Protocolsin Molecular Biology (Green and Wiley and Sons, NY, 1993).

In general, for expression of a soluble hybrid Fcγ receptor polypeptide,a DNA sequence encoding the polypeptide is operably linked to othergenetic elements required for its expression, generally including atranscription promoter and terminator, within an expression vector. Thevector will also commonly contain one or more selectable markers and oneor more origins of replication, although those skilled in the art willrecognize that within certain systems selectable markers may be providedon separate vectors, and replication of the exogenous DNA may beprovided by integration into the host cell genome. Selection ofpromoters, terminators, selectable markers, vectors and other elementsis a matter of routine design within the level of ordinary skill in theart. Many such elements are described in the literature and areavailable through commercial suppliers.

To direct a polypeptide fusion into the secretory pathway of a hostcell, a secretory signal sequence is provided in the expression vector.The secretory signal sequence may be that of a native Fcγ receptor(e.g., a native FcγRIA, FcγRIIA, FcγRIIB, FcγRIIIA, or FcγRIIB fromwhich the hybrid receptor may be derived), or may be derived fromanother secreted protein (e.g., t-PA; see U.S. Pat. No. 5,641,655) orsynthesized de novo. An engineered cleavage site may be included at thejunction between the secretory peptide and the remainder of thepolypeptide fusion to optimize proteolytic processing in the host cell.The secretory signal sequence is operably linked to the DNA sequenceencoding the polypeptide fusion, i.e., the two sequences are joined inthe correct reading frame and positioned to direct the newly synthesizedpolypeptide fusion into the secretory pathway of the host cell.Secretory signal sequences are commonly positioned 5′ to the DNAsequence encoding the polypeptide of interest, although certain signalsequences may be positioned elsewhere in the DNA sequence of interest(see, e.g., Welch et al., U.S. Pat. No. 5,037,743; Holland et al., U.S.Pat. No. 5,143,830). Exemplary secretory signal sequences for use inaccordance with the present invention include, for example, DNAsequences encoding amino acid residues 1-38 of SEQ ID NO:40, amino acidresidues 1-47 of SEQ ID NO:42, amino acid residues 1-17 or 1-20 of SEQID NO:44, amino acid residues 1-17 or 1-20 of SEQ ID NO:46, amino acidresidues 1-35 of SEQ ID NO:60, amino acid residues 1-16 of SEQ ID NO:62,amino acid residues 1-19 of SEQ ID NO:64, or amino acid residues 1-23 ofSEQ ID NO:66.

Cultured mammalian cells are suitable hosts for use within the presentinvention. Methods for introducing exogenous DNA into mammalian hostcells include calcium phosphate-mediated transfection (Wigler et al.,Cell 14:725, 1978; Corsaro and Pearson, Somatic Cell Genetics 7:603,1981: Graham and Van der Eb, Virology 52:456, 1973), electroporation(Neumann et al., EMBO J. 1:841-845, 1982), DEAE-dextran mediatedtransfection (Ausubel et al., supra), and liposome-mediated transfection(Hawley-Nelson et al., Focus 15:73, 1993; Ciccarone et al., Focus 15:80,1993). The production of recombinant polypeptides in cultured mammaliancells is disclosed by, for example, Levinson et al., U.S. Pat. No.4,713,339; Hagen et al., U.S. Pat. No. 4,784,950; Palmiter et al., U.S.Pat. No. 4,579,821; and Ringold, U.S. Pat. No. 4,656,134. Suitablecultured mammalian cells include the COS-1 (ATCC No. CRL 1650), COS-7(ATCC No. CRL 1651), BHK (ATCC No. CRL 1632), BHK 570 (ATCC No. CRL10314), 293 (ATCC No. CRL 1573; Graham et al., J. Gen. Virol. 36:59-72,1977) and Chinese hamster ovary (e.g., CHO-K¹, ATCC No. CCL 61;CHO-DG44, Urlaub et al., Proc. Natl. Acad. Sci. USA 77:4216-4220, 1980)cell lines. Additional suitable cell lines are known in the art andavailable from public depositories such as the American Type CultureCollection, Manassas, Va. Strong transcription promoters can be used,such as promoters from SV-40, cytomegalovirus, or myeloproliferativesarcoma virus. See, e.g., U.S. Pat. No. 4,956,288 and U.S. PatentApplication Publication No. 20030103986. Other suitable promotersinclude those from metallothionein genes (U.S. Pat. Nos. 4,579,821 and4,601,978) and the adenovirus major late promoter. Expression vectorsfor use in mammalian cells include pZP-1, pZP-9, and pZMP21, which havebeen deposited with the American Type Culture Collection, 10801University Blvd., Manassas, Va. USA under accession numbers 98669,98668, and PTA-5266, respectively, and derivatives of these vectors.

Drug selection is generally used to select for cultured mammalian cellsinto which foreign DNA has been inserted. Such cells are commonlyreferred to as “transfectants.” Cells that have been cultured in thepresence of the selective agent and are able to pass the gene ofinterest to their progeny are referred to as “stable transfectants.” Anexemplary selectable marker is a gene encoding resistance to theantibiotic neomycin. Selection is carried out in the presence of aneomycin-type drug, such as G-418 or the like. Selection systems canalso be used to increase the expression level of the gene of interest, aprocess referred to as “amplification.” Amplification is carried out byculturing transfectants in the presence of a low level of the selectiveagent and then increasing the amount of selective agent to select forcells that produce high levels of the products of the introduced genes.An exemplary amplifiable selectable marker is dihydrofolate reductase,which confers resistance to methotrexate. Other drug resistance genes(e.g., hygromycin resistance, multi-drug resistance, puromycinacetyltransferase) can also be used. Cell-surface markers and otherphenotypic selection markers can be used to facilitate identification oftransfected cells (e.g., by fluorescence-activated cell sorting), andinclude, for example, CD8, CD4, nerve growth factor receptor, greenfluorescent protein, and the like.

Other higher eukaryotic cells can also be used as hosts, includinginsect cells, plant cells and avian cells. The use of Agrobacteriumrhizogenes as a vector for expressing genes in plant cells has beenreviewed by Sinkar et al., J. Biosci. (Bangalore) 11:47-58, 1987.Transformation of insect cells and production of foreign polypeptidestherein is disclosed by Guarino et al., U.S. Pat. No. 5,162,222 and WIPOpublication WO 94/06463.

Insect cells can be infected with recombinant baculovirus, commonlyderived from Autographa californica nuclear polyhedrosis virus (AcNPV).See King and Possee, The Baculovirus Expression System: A LaboratoryGuide (Chapman & Hall, London); O'Reilly et al., Baculovirus ExpressionVectors: A Laboratory Manual (Oxford University Press., New York, 1994);and Richardson, Ed., Baculovirus Expression Protocols, Methods inMolecular Biology (Humana Press, Totowa, N.J., 1995). Recombinantbaculovirus can also be produced through the use of a transposon-basedsystem described by Luckow et al. (J. Virol. 67:4566-4579, 1993). Thissystem, which utilizes transfer vectors, is commercially available inkit form (BAC-TO-BAC kit; Life Technologies, Gaithersburg, Md.). Thetransfer vector (e.g., PFASTBAC1; Life Technologies) contains a Tn7transposon to move the DNA encoding the protein of interest into abaculovirus genome maintained in E. coli as a large plasmid called a“bacmid.” See Hill-Perkins and Possee, J. Gen. Virol. 71:971-976, 1990;Bonning et al., J. Gen. Virol. 75:1551-1556, 1994; and Chazenbalk andRapoport, J. Biol. Chem. 270:1543-1549, 1995. Using techniques known inthe art, a transfer vector encoding a polypeptide fusion is transformedinto E. coli host cells, and the cells are screened for bacmids whichcontain an interrupted lacZ gene indicative of recombinant baculovirus.The bacmid DNA containing the recombinant baculovirus genome isisolated, using common techniques, and used to transfect Spodopterafrugiperda cells, such as Sf9 cells. Recombinant virus that expressesthe polypeptide fusion is subsequently produced. Recombinant viralstocks are made by methods commonly used the art.

For protein production, the recombinant virus is used to infect hostcells, typically a cell line derived from the fall armyworm, Spodopterafrugiperda (e.g., Sf9 or Sf21 cells) or Trichoplusia ni (e.g., HIGH FIVEcells; Invitrogen, Carlsbad, Calif.). See generally Glick and Pasternak,supra. See also U.S. Pat. No. 5,300,435. Serum-free media are used togrow and maintain the cells. Suitable media formulations are known inthe art and can be obtained from commercial suppliers. The cells aregrown up from an inoculation density of approximately 2−5×105 cells to adensity of 1−2×10⁶ cells, at which time a recombinant viral stock isadded at a multiplicity of infection (MOI) of 0.1 to 10, more typicallynear 3. Procedures used are generally described in available laboratorymanuals (e.g., King and Possee, supra; O'Reilly et al., supra;Richardson, supra).

Fungal cells, including yeast cells, can also be used within the presentinvention. Yeast species of particular interest in this regard includeSaccharomyces cerevisiae, Pichia pastoris, and Pichia methanolica.Methods for transforming S. cerevisiae cells with exogenous DNA andproducing recombinant polypeptides therefrom are disclosed by, forexample, Kawasaki, U.S. Pat. No. 4,599,311; Kawasaki et al., U.S. Pat.No. 4,931,373; Brake, U.S. Pat. No. 4,870,008; Welch et al., U.S. Pat.No. 5,037,743; and Murray et al., U.S. Pat. No. 4,845,075. Transformedcells are selected by phenotype determined by the selectable marker,commonly drug resistance or the ability to grow in the absence of aparticular nutrient (e.g., leucine). An exemplary vector system for usein Saccharomyces cerevisiae is the POTI vector system disclosed byKawasaki et al. (U.S. Pat. No. 4,931,373), which allows transformedcells to be selected by growth in glucose-containing media. Suitablepromoters and terminators for use in yeast include those from glycolyticenzyme genes (see, e.g., Kawasaki, U.S. Pat. No. 4,599,311; Kingsman etal., U.S. Pat. No. 4,615,974; and Bitter, U.S. Pat. No. 4,977,092) andalcohol dehydrogenase genes. See also U.S. Pat. Nos. 4,990,446;5,063,154; 5,139,936; and 4,661,454. Transformation systems for otheryeasts, including Hansemdla polymorpha, Schizosaccharomyces pombe,Kluyveromyces lactis, Kluyveromyces fragilis, Ustilago maydis, Pichiapastoris, Pichia methanolica, Pichia guillermondii, and Candida maltosaare known in the art. See, e.g., Gleeson et al., J. Gen. Microbiol.132:3459-3465, 1986; Cregg, U.S. Pat. No. 4,882,279; and Raymond et al.,Yeast 14:11-23, 1998. Aspergillus cells may be utilized according to themethods of McKnight et al., U.S. Pat. No. 4,935,349. Methods fortransforming Acremonium chrysogenum are disclosed by Sumino et al., U.S.Pat. No. 5,162,228. Methods for transforming Neurospora are disclosed byLambowitz, U.S. Pat. No. 4,486,533. Production of recombinant proteinsin Pichia methanolica is disclosed in U.S. Pat. Nos. 5,716,808;5,736,383; 5,854,039; and 5,888,768.

Prokaryotic host cells, including strains of the bacteria Escherichiacoli, Bacillus, and other genera are also useful host cells within thepresent invention. Techniques for transforming these hosts andexpressing foreign DNA sequences cloned therein are well known in theart (see, e.g., Sambrook et al., supra). When expressing a polypeptidefusion in bacteria such as E. coli, the polypeptide may be retained inthe cytoplasm, typically as insoluble granules, or may be directed tothe periplasmic space by a bacterial secretion sequence. In the formercase, the cells are lysed, and the granules are recovered and denaturedusing, for example, guanidine HCl or urea. The denatured polypeptide canthen be refolded by diluting the denaturant, such as by dialysis againsta solution of urea and a combination of reduced and oxidizedglutathione, followed by dialysis against a buffered saline solution. Inthe alternative, the protein may be recovered from the cytoplasm insoluble form and isolated without the use of denaturants. The protein isrecovered from the cell as an aqueous extract in, for example, phosphatebuffered saline. To capture the protein of interest, the extract isapplied directly to a chromatographic medium, such as an immobilizedantibody or heparin-Sepharose column. Secreted polypeptides can berecovered from the periplasmic space in a soluble and functional form bydisrupting the cells (by, for example, sonication or osmotic shock) andrecovering the protein, thereby obviating the need for denaturation andrefolding. See, e.g., Lu et al., J. Immunol. Meth. 267:213-226, 2002.

Transformed or transfected host cells are cultured according toconventional procedures in a culture medium containing nutrients andother components required for the growth of the chosen host cells. Avariety of suitable media, including defined media and complex media,are known in the art and generally include a carbon source, a nitrogensource, essential amino acids, vitamins and minerals. Media may alsocontain such components as growth factors or serum, as required. Thegrowth medium will generally select for cells containing the exogenouslyadded DNA by, for example, drug selection or deficiency in an essentialnutrient which is complemented by the selectable marker carried on theexpression vector or co-transfected into the host cell.

Proteins of the present invention are purified by conventional proteinpurification methods, typically by a combination of chromatographictechniques. See generally Affinity Chromatography: Principles & Methods(Pharmacia LKB Biotechnology, Uppsala, Sweden, 1988); and Scopes,Protein Purification: Principles and Practice (Springer-Verlag, NewYork, 1994). Proteins comprising an immunoglobulin heavy chainpolypeptide can be purified by affinity chromatography on immobilizedprotein A. Additional purification steps, such as gel filtration, can beused to obtain the desired level of purity or to provide for desalting,buffer exchange, and the like.

The polypeptides of the present invention can be purified to at leastabout 80% purity, to at least about 90% purity, to at least about 95%purity, or greater than 95%, such as 96%, 97%, 98%, or greater than 99%purity with respect to contaminating macromolecules, particularly otherproteins and nucleic acids, and free of infectious and pyrogenic agents.The polypeptides of the present invention may also be purified to apharmaceutically pure state, which is greater than 99.9% pure. Incertain preparations, purified polypeptide is substantially free ofother polypeptides, particularly other polypeptides of animal origin.

In general, ammoniurm sulfate precipitation and acid or chaotropeextraction may be used for fractionation of samples. Exemplarypurification steps may include hydroxyapatite, size exclusion, FPLC andreverse-phase high performance liquid chromatography. Suitablechromatographic media include derivatized dextrans, agarose, cellulose,polyacrylamide, specialty silicas, and the like. PEI, DEAE, QAE and Qderivatives are suitable. Exemplary chromatographic media include thosemedia derivatized with phenyl, butyl, or octyl groups, such asPhenyl-Sepharose FF (Pharmacia), Toyopearl butyl 650 (Toso Haas,Montgomeryville, Pa.), Octyl-Sepharose (Pharmacia) and the like; orpolyacrylic resins, such as Amberchrom CG 71 (Toso Haas) and the like.Suitable solid supports include glass beads, silica-based resins,cellulosic resins, agarose beads, cross-linked agarose beads,polystyrene beads, cross-linked polyacrylamide resins and the like thatare insoluble under the conditions in which they are to be used. Thesesupports may be modified with reactive groups that allow attachment ofproteins by amino groups, carboxyl groups, sulfhydryl groups, hydroxylgroups and/or carbohydrate moieties.

Examples of coupling chemistries include cyanogen bromide activation,N-hydroxysuccinimide activation, epoxide activation, sulfhydrylactivation, hydrazide activation, and carboxyl and amino derivatives forcarbodiimide coupling chemistries. These and other solid media are wellknown and widely used in the art, and are available from commercialsuppliers. Selection of a particular method for polypeptide isolationand purification is a matter of routine design and is determined in partby the properties of the chosen support See, for example, AffinityChromatography: Principles & Methods (Pharmacia LKB Biotechnology 1988),and Doonan, Protein Purification Protocols (The Humana Press 1996).

Additional variations of soluble FcγR isolation and purification can bedevised by those of skill in the art. For example, anti-FcγR antibodiescan be used to isolate large quantities of protein by immunoaffinitypurification.

The polypeptides of the present invention can also be isolated byexploitation of particular properties. For example, immobilized metalion adsorption (IMAC) chromatography can be used to purifyhistidine-rich proteins, including those comprising polyhistidine tags.Briefly, a gel is first charged with divalent metal ions to form achelate (Sulkowski, Trends in Biochem. 3:1 (1985)). Histidine-richproteins will be adsorbed to this matrix with differing affinities,depending upon the metal ion used, and will be eluted by competitiveelution, lowering the pH, or use of strong chelating agents. Othermethods of purification include purification of glycosylated proteins bylectin affinity chromatography and ion exchange chromatography (M.Deutscher (ed), Meth. Enzymol. 182:529, 1990). Within additionalembodiments of the invention, a fusion of the polypeptide of interestand an affinity tag (e.g., maltose-binding protein, an immunoglobulindomain, substance P, Flag™ peptide, or another polypeptide or proteinfor which an antibody or other specific binding agent is available) maybe constructed to facilitate purification.

Soluble hybrid FcγR polypeptides or fragments thereof may also beprepared through chemical synthesis, as described above. The FcγRpolypeptides may be monomers or multimers (e.g., homodimers);glycosylated or non-glycosylated; PEGylated or non-PEGylated; and may ormay not include an initial methionine amino acid residue.

In some variations, a soluble hybrid FcγR polypeptide is chemicallymodified via linkage to a polymer. Typically, the polymer is watersoluble so that the hybrid FcγR polypeptide conjugate does notprecipitate in an aqueous environment, such as a physiologicalenvironment. An example of a suitable polymer is one that has beenmodified to have a single reactive group, such as an active ester foracylation, or an aldehyde for alkylation. In this way, the degree ofpolymerization can be controlled. The polymer may be branched orunbranched. A hybrid FcγR polypeptide conjugate can also comprise amixture of such water-soluble polymers. General methods for producingconjugates comprising a polypeptide and water-soluble polymer moietiesare known in the art. (See, e.g., U.S. Pat. No. 5,382,657 to Karasiewiczet al.; U.S. Pat. No. 5,738,846 to Greenwald et al.; Nieforth et al.,Clin. Pharmacol. Ther. 59:636, 1996; Monkarsh et al., Anal. Biochem.247:434, 1997.) Such methods can be employed for making hybridFcIR-comprising homodimeric, heterodimeric or multimeric solublereceptor conjugates.

One example of a soluble hybrid FcγR polypeptide conjugate comprises apolyalkyl oxide moiety attached to the N-terminus of the FcγRpolypeptide. PEG is one suitable polyalkyl oxide. As an illustration,soluble hybrid FcγR can be modified with PEG, a process known as“PEGylation.” PEGylation of soluble hybrid FcγR can be carried out byany of the PEGylation reactions known in the art. (See, e.g., EP 0 154316; Delgado et al., Critical Reviews in Therapeutic Drug CarrierSystems 9:249, 1992; Duncan and Spreafico, Clin. Pharmacokinet. 27.290,1994; Francis et al., Int J Hematol 68:1, 1998.) For example, PEGylationcan be performed by an acylation reaction or by an alkylation reactionwith a reactive polyethylene glycol molecule. In an alternativeapproach, hybrid FcγR conjugates are formed by condensing activated PEG,in which a terminal hydroxy or amino group of PEG has been replaced byan activated linker. (See, e.g., U.S. Pat. No. 5,382,657 to Karasiewiczet al.) For PEGylation reactions, the typical molecular weight of apolymer molecule is about 2 kDa to about 100 kDa, about 5 kDa to about50 kDa, or about 12 kDa to about 25 kDa. The molar ratio ofwater-soluble polymer to soluble hybrid FcγR will generally be in therange of 1:1 to 100:1. Typically, the molar ratio of water-solublepolymer to soluble hybrid FcγR will be 1:1 to 20:1 for polyPEGylation,and 1:1 to 5:1 for monoPEGylation.

III. Methods and Compositions for Using Soluble Hybrid Fcγ Receptors

The soluble hybrid FcγR polypeptides of the present invention actspecifically against IgG and can inhibit IgG binding to an Fcγ receptor,and are thus useful for inhibiting IgG and Fcγ receptor activity.Accordingly, in another aspect of the invention, soluble hybrid FcγRpolypeptides as described herein are used to inhibit the interactionbetween IgG and Fc receptors as well as to inhibit physiologicalcorrelates of such IgG-FcR interactions in vivo or in vitro (e.g., theprecipitation of antigen-antibody immune complexes, signal transduction,cytokine secretion from immune cells having cell-surface Fc receptors).Activity of the soluble FcγR polypeptides of the present invention canbe assayed, for example, in proliferation, luciferase, or binding assaysin the presence of IgG, as well as other biological or biochemicalassays for assessing the interaction of IgG with FcγR as describedherein or otherwise known in the art.

As shown herein, a soluble FcγRIA polypeptide completely blocked immunecomplex precipitation and also blocked the binding and signaling ofimmune complexes (described in detail in the Examples below). Moreover,soluble FcγRIA blocked inflammation in the cutaneous Arthus reaction aswell as in the collagen antibody-induced and collagen-induced models ofarthritis. These findings show that soluble FcγRIA is a potenttherapeutic that can be used to treat autoimmune disease andinflammation and further support the use of other soluble, high-affinityreceptors for Fcγ, including the hybrid Fcγ receptors as describedherein, for treating such conditions.

The soluble hybrid FcγR polypeptides of the invention are, therefore,particularly useful for modulating an immune response by binding IgG andinhibiting the binding of IgG with an endogenous Fcγ receptor.Accordingly, the present invention includes the use of soluble hybridFcγR polypeptides to treat a subject with inflammation or having animmune disease or disorder. Suitable subjects include mammals, such ashumans. The soluble hybrid FcγR polypeptides of the invention may beused for inhibiting the inflammatory effects of IgG and/or immunecomplexes in vivo, for therapeutic use against SLE, cryoglobulinemia,autoimmune thrombocytopenias (ITP and TTP), adult dermatomyositis,hepatitis-C-associated cryoglobulinemia, hepatitis-B-associatedpolyarteritis nodosa, Guillian-Barre syndrome, Goodpasture's syndrome,chronic inflammatory demyelinating polyneuropathies, anti-phospholipidantibody syndrome, vasculitis, uveitis, serum sickness, pemphigus (e.g.,pemphigus vulgaris), diseases associated with exogenous antigens,psoriasis, atopic dermatitis, inflammatory skin conditions, endotoxemia,arthritis, asthma, IBD, colitis, psoriatic arthritis, rheumatoidarthritis, or other IgG- or immune-complex-mediated inflammatoryconditions.

In certain variations, a soluble hybrid FcγR polypeptide is used totreat an IgG-mediated inflammatory condition such as, for example,systemic lupus erythematosus (SLE); lupus (including nephritis,non-renal, discoid, alopecia); cryoglobulinemia; mixed connective tissuedisease; autoimmune thrombocytopenias (idiopathic thrombocytopenicpurpura (ITP); thrombotic throbocytopenic purpura (TTP)); Sjogren'ssyndrome; adult dermatomyositis; hepatitis-C-associatedcryoglobulinemia; hepatitis-B-associated polyarteritis nodosa;Guillian-Barre syndrome; Goodpasture's syndrome; chronic inflammatorydemyelinating polyneuropathies; anti-phospholipid antibody syndrome;vasculitis; uveitis; serum sickness; diseases associated with exogenousantigens; arthritis (rheumatoid arthritis, juvenile rheumatoidarthritis, psoriatic arthritis); psoriasis; atopic dermatitis;inflammatory skin conditions; responses associated with inflammatorybowel disease (IBD) (Crohn's disease, ulcerative colitis);diverticulosis; asthma; pancreatitis; type I (juvenile onset) diabetes(IDDM); pancreatic cancer; pancreatitis; Grave's Disease; chronicautoimmune urticaria; polymyositis/dermatomyositis; toxic epidermalnecrolysis; systemic scleroderma and sclerosis; respiratory distresssyndrome; adult respiratory distress syndrome (ARDS); meningitis;allergic rhinitis; encephalitis; colitis; glomerulonephritis; anIgG-mediated allergic condition; atherosclerosis, autoimmunemyocarditis; multiple sclerosis; allergic encephalomyelitis;sarcoidosis, granulomatosis including Wegener's granulomatosis;agranulocytosis; aplastic anemia; Coombs positive anemia; DiamondBlackfan anemia; immune hemolytic anemia including autoimmune hemolyticanemia (AMHA); pernicious anemia; pure red cell aplasia (PRCA); FactorVIII deficiency; hemophilia A; autoimmune neutropenia; pancytopenia;leucopenia; diseases involving leukocyte diapedesis; a CNS inflammatorydisorder, multiple organ injury syndrome; myasthenia gravis;anti-glomerular basement membrane disease; Bechet disease; Castleman'ssyndrome; Lambert-Eaton Myasthenic Syndrome; Reynaud's syndrome;Stevens-Johnson syndrome; bone marrow transplant rejection; solid organtransplant rejection (including pretreatment for high panel reactiveantibody titers); graft-versus-host disease (GVHD); pemphigoid bullous;pemphigus (all including vulgaris, foliaceus); autoimmunepolyendocrinopathies; Reiter's disease; stiff-man syndrome; immunecomplex nephritis; an autoimmune disease of the testis or ovary such as,e.g., autoimune orchitis or oophoritis; primary hypothyroidism; anautoimmune endocrine disease such as, e.g., autoimmune thyroiditis,chronic thyroiditis (Hashimoto's Thyroiditis), subacute thyroiditis,idiopathic hypothyroidism, Addison's disease, or an autoimmunepolyglandular syndrome (or a polyglandular endocrinopathy syndrome);autoimmune hepatitis; Lymphoid interstitial pneumonitis (HIV);bronchiolitis obliterans (non-transplant) vs NSIP, large vesselvasculitis (including polymyalgia rheumatica and giant cell (Takayasu's)arteritis); medium vessel vasculitis (including Kawasaki's Disease andpolyarteritis nodosa); ankylosing spondylitis; rapidly progressiveglomerulonephritis; primary biliary cirrhosis; celiac sprue (glutenenteropathy); ALS; coronary artery disease; or another instance whereinhibition of IgG or immune complexes is desired.

The soluble hybrid FcγR polypeptides of the invention may also be usedto treat psychological disorders associated with deposition of immunecomplexes with the choroids plexus of the brain. Such deposition, forexample, may underlie the central and peripheral nervous systemmanisfestations of diseases such as Systemic Lupus Erythematosus. Insome patients, these manisfestations are a major cause of morbidity andmortality and include cognitive dysfunction, particularly difficultieswith memory and reasoning psychosis, headaches, and seizures. As anotherexample, deposition of immune complexes within the choriod plexus may beresponsible for the peripheral neuropathy seen in essential mixedcryoglobulinemia. (See Harrison's Principles of Internal Medicine(Kasper et al. eds., McGraw-Hill, New York 2005).)

In each of the embodiments of the treatment methods described herein, asoluble hybrid FcγR polypeptide is delivered in a manner consistent withconventional methodologies associated with management of the disease ordisorder for which treatment is sought. In accordance with thedisclosure herein, an effective amount of the agent is administered to asubject in need of such treatment for a time and under conditionssufficient to prevent or treat the disease or disorder.

Subjects for administration of soluble hybrid FcγR polypeptides asdescribed herein include patients at high risk for developing aparticular IgG-mediated inflammatory condition as well as patientspresenting with an existing IgG-mediated inflammatory condition. Incertain embodiments, the subject has been diagnosed as having thedisease or disorder for which treatment is sought. Further, subjects canbe monitored during the course of treatment for any change in thedisease or disorder (e.g., for an increase or decrease in clinicalsymptoms of the disease or disorder). Also, in some variations, thesubject does not suffer from another disease or disorder requiringtreatment that involves inhibiting the interaction of IgG with an Feyreceptor.

In prophylactic applications, pharmaceutical compositions or medicantsare administered to a patient susceptible to, or otherwise at risk of, aparticular disease in an amount sufficient to eliminate or reduce therisk or delay the outset of the disease. In therapeutic applications,compositions or medicants are administered to a patient suspected of, oralready suffering from such a disease in an amount sufficient to cure,or at least partially arrest, the symptoms of the disease and itscomplications. An amount adequate to accomplish this is referred to as atherapeutically- or pharmaceutically-effective dose or amount. In bothprophylactic and therapeutic regimes, a soluble hybrid FcγR polypeptideof the invention is usually administered in several dosages until asufficient response (e.g., inhibition of inflammatory mediatorsassociated with the interaction of IgG with FcγR or with IC deposition)has been achieved. Typically, the response is monitored and repeateddosages are given if the desired response starts to fade.

To identify subject patients for treatment according to the methods ofthe invention, accepted screening methods may be employed to determinerisk factors associated with specific IgG-mediated inflammatoryconditions or to determine the status of an existing disorder identifiedin a subject. Such methods can include, for example, determining whetheran individual has relatives who have been diagnosed with a particulardisease. Screening methods can also include, for example, conventionalwork-ups to determine familial status for a particular disease known tohave a heritable component Toward this end, nucleotide probes can beroutinely employed to identify individuals carrying genetic markersassociated with a particular disease of interest. In addition, a widevariety of immunological methods are known in the art that are useful toidentify markers for specific diseases. For example, various ELISAimmunoassay methods are available and well-known in the art that employmonoclonal antibody probes to detect antigens or autoantibodiesassociated with specific inflammatory diseases. Screening may beimplemented as indicated by known patient symptomology, age factors,related risk factors, etc. These methods allow the clinician toroutinely select patients in need of the methods described herein fortreatment. In accordance with these methods, inhibition of IgG-mediatedinflammation may be implemented as an independent treatment program oras a follow-up, adjunct, or coordinate treatment regimen to othertreatments.

For administration, a soluble hybrid FcγR polypeptide is formulated as apharmaceutical composition. A pharmaceutical composition comprising asoluble hybrid FcγR polypeptide can be formulated according to knownmethods to prepare pharmaceutically useful compositions, whereby thetherapeutic molecule is combined in a mixture with a pharmaceuticallyacceptable carrier. A composition is said to be a “pharmaceuticallyacceptable carrier” if its administration can be tolerated by arecipient patient. Pharmaceutically acceptable carriers can be aqueous,lipidic, semi-solid or solid as appropriate to the condition to betreated and mode of delivery. Pharmaceutically acceptable aqueouscarriers include, without limitation, saline, buffered saline (e.g.,phosphate-buffered saline), 5% dextrose in water, and the like. Othersuitable carriers are well-known to those in the art (See, e.g.,Gemnnaro (ed.), Remington's Pharmaceutical Sciences (Mack PublishingCompany, 19th ed. 1995).) Formulations may further include one or moreexcipients, preservatives, solubilizers, buffering agents, albumin toprevent protein loss on vial surfaces, etc.

A pharmaceutical composition comprising a soluble hybrid FcγRpolypeptide of the invention is administered to a subject in aneffective amount. Accordingly, the composition is generally administeredin an amount that produces a statistically significant beneficialeffect, such as a statistically significant moderation or reversal ofthe progression or severity of a disease. The exact dose will bedetermined by the clinician according to accepted standards, taking intoaccount the nature and severity of the condition to be treated, patienttraits, etc. Determination of dose is within the level of ordinary skillin the art. According to the methods of the present invention, thepolypeptide may be administered to subjects by a variety ofadministration modes, including, for example, by intramuscular,subcutaneous, intravenous, intra-atrial, intra-articular, parenteral,intranasal, intrapulmonary, transdermal, intrapleural, intrathecal, andoral routes of administration. For prevention and treatment purposes,depending on the route and method of administration, the soluble hybridFcγR polypeptide may be administered to a subject in a single bolusdelivery, via continuous delivery over an extended time period (e.g.,continuous transdermal delivery or as a prolonged infusion), or in arepeated administration protocol (e.g., on an hourly, daily, or weeklybasis). Intravenous administration will be by bolus injection orinfusion over a typical period of one to several hours. Sustainedrelease formulations can be employed.

Determination of effective dosages is typically based on animal modelstudies followed up by human clinical trials and is guided bydetermining effective dosages and administration protocols thatsignificantly reduce the occurrence or severity of the subject diseaseor disorder in model subjects. Effective doses of the compositions ofthe present invention vary depending upon many different factors,including means of administration, target site, physiological state ofthe patient, whether the patient is human or an animal, othermedications administered, whether treatment is prophylactic ortherapeutic, as well as the specific activity of the composition itselfand its ability to elicit the desired response in the individual.Usually, the patient is a human, but in some diseases, the patient canbe a nonhuman mammal. Typically, dosage regimens are adjusted to providean optimum therapeutic response, i.e., to optimize safety and efficacy.Accordingly, a therapeutically or prophylactically effective amount isalso one in which any undesired collateral effects are outweighed bybeneficial effects of inhibition IgG-mediated inflammation. Foradministration of a soluble hybrid FcγR polypeptide, a dosage typicallyranges from about 0.1 μg to 100 mg/kg or 1 μg/kg to about 50 mg/kg, andmore usually 10 μg to 5 mg/kg of the subject's body weight. In morespecific embodiments, an effective amount of the agent is between about1 μg/kg and about 20 mg/kg, between about 10 μg/kg and about 10 mg/kg,or between about 0.1 mg/kg and about 5 mg/kg. Dosages within this rangecan be achieved by single or multiple administrations, including, e.g.,multiple administrations per day or daily, weekly, bi-weekly, or monthlyadministrations. For example, in certain variations, a regimen consistsof an initial administration followed by multiple, subsequentadministrations at weekly or bi-weekly intervals. Another regimenconsists of an initial administration followed by multiple, subsequentadministrations at monthly or bi-monthly intervals. Alternatively,administrations can be on an irregular basis as indicated by monitoringof IgG-mediated inflammation and/or clinical symptoms of the disease ordisorder.

Dosage of the pharmaceutical composition may be varied by the attendingclinician to maintain a desired concentration at a target site. Forexample, if an intravenous mode of delivery is selected, localconcentration of the agent in the bloodstream at the target tissue maybe between about 1-50 nanomoles of the composition per liter, sometimesbetween about 1.0 nanomole per liter and 10, 15, or 25 nanomoles perliter depending on the subject's status and projected measured response.Higher or lower concentrations may be selected based on the mode ofdelivery, e.g., trans-epidermal delivery versus delivery to a mucosalsurface. Dosage should also be adjusted based on the release rate of theadministered formulation, e.g., nasal spray versus powder, sustainedrelease oral or injected particles, transdermal formulations, etc. Toachieve the same serum concentration level, for example, slow-releaseparticles with a release rate of 5 nanomolar (under standard conditions)would be administered at about twice the dosage of particles with arelease rate of 10 nanomolar.

A pharmaceutical composition comprising a soluble hybrid FcγRpolypeptide can be furnished in liquid form, in an aerosol, or in solidform. Liquid forms, are illustrated by injectable solutions, aerosols,droplets, topological solutions and oral suspensions. Exemplary solidforms include capsules, tablets, and controlled-release forms. Thelatter form is illustrated by miniosmotic pumps and implants. (See,e.g., Bremer et al., Pharm. Biotechnol. 10:239, 1997; Ranade, “Implantsin Drug Delivery,” in Drug Delivery Systems 95-123 (Ranade andHollinger, eds., CRC Press 1995); Bremer et al., “Protein Delivery withInfusion Pumps,” in Protein belivery: Physical Systems 239-254 (Sandersand Hendren, eds., Plenum Press 1997); Yewey et al., “Delivery ofProteins from a Controlled Release Injectable Implant,” in ProteinDelivery: Physical Systems 93-117 (Sanders and Hendren, eds., PlenumPress 1997).) Other solid forms include creams, pastes, othertopological applications, and the like.

Liposomes provide one means to deliver therapeutic polypeptides to asubject, e.g., intravenously, intraperitoneally, intrathecally,intramuscularly, subcutaneously, or via oral administration, inhalation,or intranasal administration. Liposomes are microscopic vesicles thatconsist of one or more lipid bilayers surrounding aqueous compartments.(See, generally, Bakker-Woudenberg et al., Eur. J. Clin. Microbiol.Infect. Dis. 12 (Suppl. 1):S61, 1993; Kim, Drugs 46:618, 1993; Ranade,“Site-Specific Drug Delivery Using Liposomes as Carriers,” in DrugDelivery Systems 3-24 (Ranade and Hollinger, eds., CRC Press 1995).)Liposomes are similar in composition to cellular membranes and as aresult, liposomes can be administered safely and are biodegradable.Depending on the method of preparation, liposomes may be unilamellar ormultilamellar, and liposomes can vary in size with diameters rangingfrom 0.02 μm to greater than 10 μm. A variety of agents can beencapsulated in liposomes: hydrophobic agents partition in the bilayersand hydrophilic agents partition within the inner aqueous space(s).(See, e.g., Machy et al., Liposomes In Cell Biology And Pharmacology(John Libbey 1987); Ostro et al., American J. Hosp. Pharm. 46:1576,1989.) Moreover, it is possible to control the therapeutic availabilityof the encapsulated agent by varying liposome size, the number ofbilayers, lipid composition, as well as the charge and surfacecharacteristics of the liposomes.

Liposomes can adsorb to virtually any type of cell and then slowlyrelease the encapsulated agent. Alternatively, an absorbed liposome maybe endocytosed by cells that are phagocytic. Endocytosis is followed byintralysosomal degradation of liposomal lipids and release of theencapsulated agents (see Scherphof et al., Ann. N.Y. Acad. Sci. 446:368,1985). After intravenous administration, small liposomes (0.1 to 1.0 μm)are typically taken up by cells of the reticuloendothelial system,located principally in the liver and spleen, whereas liposomes largerthan 3.0 μm are deposited in the lung. This preferential uptake ofsmaller liposomes by the cells of the reticuloendothelial system hasbeen used to deliver chemotherapeutic agents to macrophages and totumors of the liver.

The reticuloendothelial system can be circumvented by several methodsincluding saturation with large doses of liposome particles, orselective macrophage inactivation by pharmacological means (see Claassenet al., Biochim. Biophys. Acta 802:428, 1984). In addition,incorporation of glycolipid- or polyethelene glycol-derivatizedphospholipids into liposome membranes has been shown to result in asignificantly reduced uptake by the reticuloendothelial system (seeAllen et al., Biochim. Biophys. Acta 1068:133, 1991; Allen et al.,Biochim. Biophys. Acta 1150:9, 1993).

Liposomes can also be prepared to target particular cells or organs byvarying phospholipid composition or by inserting receptors orcounter-receptors into the liposomes. For example, liposomes, preparedwith a high content of a nonionic surfactant, have been used to targetthe liver. (See, e.g., Japanese Patent 04-244,018 to Hayakawa et al.;Kato et al., Biol. Pharm. Bull. 16:960, 1993.) These formulations wereprepared by mixing soybean phospatidylcholine, α-tocopherol, andethoxylated hydrogenated castor oil (HCO-60) in methanol, concentratingthe mixture under vacuum, and then reconstituting the mixture withwater. A liposomal formulation of dipalmitoylphosphatidylcholine (DPPC)with a soybean-derived sterylglucoside mixture (SG) and cholesterol (Ch)has also been shown to target the liver. (See Shimizu et al., Biol.Pharm. Bull. 20:881, 1997.)

Alternatively, various targeting counter-receptors can be bound to thesurface of the liposome, such as antibodies, antibody fragments,carbohydrates, vitamins, and transport proteins. For example, fortargeting to the liver, liposomes can be modified with branched typegalactosyllipid derivatives to target asialoglycoprotein (galactose)receptors, which are exclusively expressed on the surface of livercells. (See Kato and Sugiyama, Crit. Rev. Ther. Drug Carrier Syst.14:287, 1997; Murahashi et al., Biol. Pharm. Bull. 20:259, 1997.) In amore general approach to tissue targeting, target cells are prelabeledwith biotinylated antibodies specific for a counter-receptor expressedby the target cell. (See Harasym et al., Adv. Drug Deliv. Rev. 32:99,1998.) After plasma elimination of free antibody,streptavidin-conjugated liposomes are administered. In another approach,targeting antibodies are directly attached to liposomes. (See Harasym etal., supra.)

Polypeptides of the present invention can be encapsulated withinliposomes using standard techniques of protein microencapsulation. (See,e.g., Anderson et al., Infect. Immun. 31:1099, 1981; Anderson et al.,Cancer Res. 50:1853, 1990; Cohen et al., Biochim. Biophys. Acta 1063:95,1991; Alving et al. “Preparation and Use of Liposomes in ImmunologicalStudies,” in Liposome Technology (Vol. III) 317 (Gregoriadis, ed., CRCPress, 2nd ed. 1993); Wassef et al., Meth. Enzymol. 149:124, 1987.) Asnoted above, therapeutically useful liposomes may contain a variety ofcomponents. For example, liposomes may comprise lipid derivatives ofpoly(ethylene glycol). (See Allen et al., Biochim. Biophys. Acta 1150:9,1993.)

Degradable polymer micro spheres have been designed to maintain highsystemic levels of therapeutic proteins. Microspheres are prepared fromdegradable polymers such as poly(lactide-co-glycolide) (PLG),polyanhydrides, poly (ortho esters), nonbiodegradable ethylvinyl acetatepolymers, in which proteins are entrapped in the polymer. (See, e.g.,Gombotz and Pettit, Bioconjugate Chem. 6:332, 1995; Ranade, “Role ofPolymers in Drug Delivery,” in Drug Delivery Systems 51-93 (Ranade andHollinger, eds., CRC Press 1995); Roskos and Maskiewicz, “DegradableControlled Release Systems Useful for Protein Delivery,” in ProteinDelivery: Physical Systems 45-92 (Sanders and Hendren, eds., PlenumPress 1997); Bartus et al., Science 281:1161, 1998; Putney and Burke,Nature Biotechnology 16:153, 1998; Putney, Curr. Opin. Chem. Biol.2:548, 1998.) Polyethylene glycol (PEG)-coated nanospheres can alsoprovide carriers for intravenous administration of therapeutic proteins.(See. e.g., Gref et al., Pharm. Biotechnol. 10:167, 1997.)

Other dosage forms can be devised by those skilled in the art, as shownby, e.g., Ansel and Popovich, Pharmaceutical Dosage Forms and DrugDelivery Systems (Lea & Febiger, 5th ed. 1990); Gennaro (ed.),Remington's Pharmaceutical Sciences (Mack Publishing Company, 19th ed.1995), and Ranade and Hollinger, Drug Delivery Systems (CRC Press 1996).

Pharmaceutical compositions may be supplied as a kit comprising acontainer that comprises a soluble FcγR polypeptide of the invention.The FcγR polypeptides of the invention can be provided in the form of aninjectable solution for single or multiple doses, or as a sterile powderthat will be reconstituted before injection. Alternatively, such a kitcan include a dry-powder disperser, liquid aerosol generator, ornebulizer for administration of a therapeutic polypeptide. Such a kitmay further comprise written information on indications and usage of thepharmaceutical composition. Moreover, such information may include astatement that the soluble hybrid FcγR polypeptide-comprisingcomposition is contraindicated in patients with a known hypersensitivityto FcγR.

As discussed above, the soluble hybrid FcγR polypeptides of theinvention have therapeutic potential for a wide variety of IgG-mediatedinflammatory diseases. Inflammation—a protective response by an organismto fend off an invading agent—is a cascading event that involves manycellular and humoral mediators. On one hand, suppression of inflammatoryresponses can leave a host immunocompromised; if left unchecked,however, inflammation can lead to serious complications including, forexample, chronic inflammatory diseases. Importantly, these diversedisease states share common inflammatory mediators. The collectivediseases that are characterized by inflammation have a large impact onhuman morbidity and mortality. The studies described herein show, interalia, the ability of soluble FcγR to block the binding and signaling ofimmune complexes, as well as the ability of soluble FcγR to treatIgG-mediated disease. Thus, the soluble hybrid FcγR polypeptides of theinvention have therapeutic potential for a vast number of human andanimal diseases such as, for example, the IgG- andimmune-complex-mediated diseases discussed herein. Exemplary diseasesamenable to treatment using soluble hybrid FcγR are further described inSections III(A) and III(B), infra.

A. Immune-complex-Mediated Diseases

The binding of an antigen with its cognate antibody generates immunecomplexes, and deposition of these immune complexes within tissues isthe pathogenic mechanism underlying a variety of autoimmune diseases(see Jancar and Crespo, Trends Immunol. 26:48-55, 2005). These diseasesinclude the connective tissue autoimmune diseases such as systemic lupuserythematosus (SLE), dermatomyositis, rheumatoid arthritis, Sjogren'ssyndrome, and mixed connective tissue disease; diseases of diverseetiology such as cryoglobulinemia, polyarteritis nodosa, and theanti-phospholipid syndrome; as well as diseases associated withexogenous antigens including bacterial, viral, and parasitic infections,diseases associated with organic dusts, and serum sickness type ofdiseases including passive immunotherapy for infection, venomous snakebites, and drug hypersensitivity. While each of these conditions iscaused by and exhibits specific antigen-antibody pairs, the mechanismfor tissue damage is similar: the formation of circulating immunecomplexes, followed by their deposition within tissues (see Jancar andCrespo, supra). Antigen-antibody complexes can damage tissues bytriggering inflammation, a process mediated in part through the bindingof immune complexes to cell surface Fcγ receptors and by their abilityto fix complement.

In the normal situation, immune complexes are cleared by phagocyticcells of the reticuloendothelial system. In some instances, however,immune complexes accumulate and deposit in tissues, causing type IIIhypersensitivity reactions. (See Jancar and Crespo, supra.) When immunecomplexes form in the blood, deposition can occur at sites removed fromthe site of antigen entry. Complex deposition is routinely observed,e.g., on blood vessel walls, in the synovial membranes of joints, on theglomerular basement membrane of the kidney, and on the choroid plexus ofthe brain, sites where filtration of plasma occurs. (See Jancar andCrespo, supra.) This is the reason for the high incidence of arthritis,vasculitis, and glomerulonephritis observed in immune complex-mediateddiseases, such as cryoglobulinemia.

Following their deposition within tissues, immune complexes bind to cellsurface FcγR via the Fc domain of IgG. As previously noted, FcγR play acrucial role as a link between the humoral and cellular arms of theimmune system (see Coben-Solal et al., Immunol. Lett. 92:199-205, 2004;Hogarth et al., Curr. Opin. Immunol. 14:798-802, 2002; Nakamura et al.,Expert Opin. Ther. Targets 9:169-190, 2005; Nimmerjahn, Springer Semin.Immunopathol. 28:305-319, 2006). Ligation of these cell surfacereceptors by the Fc portion of IgG can trigger a variety of immuneeffector functions such as antigen presentation, antibody dependentcellular cytotoxicity (ADCC), phagocytosis, and the release ofinflammatory mediators. The three main classes of Fcγ receptors—FcγRI,FcγRII, and FcRγIII—are expressed within specific and overlappingsubsets of cells of the human immune system, expression patterns thataccount for their diverse roles in immune homeostasis (see Nakamura etal., supra). With the exception of FcγRI, which exhibits a high affinityfor monomeric IgG, the other subclasses of FcγRs are low affinity IgGreceptors. (See Cohen-Solal et al., supra; Hogarth et al., supra.)However, these cellular receptors bind antigen-antibody immune complexes(IC) with high avidity, through multiple Fc:FcγR interactions. Thisproperty is thought to allow cells expressing FcγRII and/or FcγRIII tosample their extracellular environment and respond appropriately to ICin the face of saturating amounts of monomeric IgG. (See Hogarth et al.,supra.)

As part of a screening effort to identify soluble receptorsdemonstrating this ability, the soluble extracellular domains of each ofthe human native FcγR were expressed in CHO cells and purified tohomogeneity from their conditioned media. While each of the rh-FcγRreduced immune complex-mediated inflammatory events in several in vitrosystems, only the high affinity receptor, FcγRIA, produced consistentreductions in inflammation in the cutaneous reverse passive Arthusreaction in mice. This result was unexpected in that FcγRIA, as a highaffinity receptor for monomeric IgG, was generally expected to besaturated with circulating monomeric IgG in vivo and thus unavailablefor binding to IC. The observation that systemic delivery of FcγRIA alsoabolished inflammation in the murine collagen antibody-induced model ofarthritis suggests that FcγRIA may be a novel therapy for treatingimmune complex-mediated diseases. Further, these results support the useof other soluble, high-affinity receptors for Fcγ, including the hybridFcγ receptors as described herein, for treating such conditions.

Accordingly, by blocking the binding of immune complexes to cell surfaceFc gamma receptors, the soluble hybrid FcγR polypeptides of theinvention can reduce inflammatory cytokine secretion and reduceinfiltration of inflammatory cell types such as neutrophils. Asdemonstrated by studies described herein, soluble FcγRIA blocked theprecipitation of antigen antibody immune complexes and inhibited immunecomplex-mediated cytokine secretion by mast cells (see Examples 9 and10, infra). In studies in mice, moreover, soluble FcγRIA reduced edemaand neutrophil infiltration in the cutaneous reverse passive Arthusreaction and reduced paw inflammation in the collagen antibody-inducedarthritis model and, moreover, in collagen-induced arthritis in mice.(See Examples 9-11 and 13, infra.) Thus, soluble FcγRIA, as well ashybrid forms thereof as described herein, can be used in the treatmentof various immune complex-mediated diseases in humans or other non-humanspecies.

1. Cryoblobulinemia

The term cryoglobulinemia refers to the presence in serum of one(monoclonal cryoglobulinemia) or more (mixed cryoglobulinemia)immunoglobulins that reversibly precipitate at temperatures below 37° C.(See Meltzer and Franklin, Am. J. Med. 40:828-836, 1996; Dammacco etal., Eur. J. Clin. Invest. 31:628-638, 2001; Sansonno et al.,Rheumatology (Oxford) 46:572-578, 2007). The mechanism ofcryoprecipitation is obscure but may involve alterations in Igstructure, self-association of Ig Fc domains, and/or IgM rheumatoidfactor activity. (See Sansonno and Dammacco, Lancet Infect. Dis.5:227-236, 2005.) Cryoglobulinemia is classified into three subgroups(see Dammacco et al., supra): Type I is composed of a single monoclonalIg; Type II is composed of a mixture of monoclonal IgM and polyclonalIgG; and Type III is a mixture of polyclonal IgM/IgG. Cryoglobulinemiatypes I, II, and III account for approximately 10-15%, 50-60%, and30-40%, of all people with serum cryoprecipitates, respectively. (SeeDammacco et al., supra; Sansonno et al., supra.)

Patients with cryogobulinemia present most often with a clinical triadof purpura, weakness, and arthralgias, as well as glomerulonephritis,vasculitis, peripheral neuropathy, arthritis, and/or pulmonary symptomsof hemoptysis and dyspnea. (See Dammacco et al., supra; Sansonno et al.,supra; Ferri et al., Cleve. Clin. J. Med. 69 Suppl 2:SII20-23, 2002(“Ferri et al. I”); Ferri et al, J. Clin. Pathol. 55:4-13, 2002 (“Ferriet al. II”).) Cryoglobulinemia can be observed in association of avariety of disorders including multiple myeloma, lymphoproliferativedisorders, connective tissue diseases, infection, and liver disease.(Ferri et al. I, supra; Ferri et al. II, supra.) Before the discovery ofhepatitis C virus (HCV) and prior to development of methods to detectanti-HCV antibodies, patients without identifiable underlying diseasewere considered to have idiopathic or “essential” mixedcryoglobulinemia. It is now known that “essential” mixedcryoglobulinemia is strongly associated with HCV infection andencompasses the majority of patients with types II and IIIcryoglobulinemia. (See Sansonno et al., supra.) Current evidencesuggests that essential mixed cryoglobulinemia occurs when an aberrantimmune response to hepatitis C infection leads to the formation ofimmune complexes consisting of hepatitis C antigens, polyclonalhepatitis C-specific IgG, and monoclonal IgM rheumatoid factor. Thedeposition of these immune complexes within susceptible tissue sitestriggers an inflammatory cascade that results in the clinical syndromeof essential mixed cryoglobulinemia. (Dammacco et al., supra; Sansonnoet al., supra.)

Cryoglobulinemia is also associated with a variety of other infectionsin addition to HCV (see Ferri et al. II, supra), including those ofviral origin such as cytomegalovirus (CMV), Epstein-Barr virus (EBV),human immunodeficiency virus (HIV-1), and hepatis B virus (HBV), thoseof bacterial origin including Mycoplasma pneuymoniae, Treponema pallidum(syphilis), Mycobacterium tuberculosis, Coxiella Burnetti Q fever,Brucella, and infections with parasites such as Toxoplasma gondii andVisceral leishmaniasis.

Essential mixed cryoglobulinemia is considered to be a primaryvasculitis disorder. The Chapel Hill Consensus Conference (CHCC)classification of vasculitis is based on the size of the affectedvessels and groups the diseases into those affecting large-, medium-, orsmall-vessels. (See Jennette et al., Cleve. Clin. J. Med. 69 Suppl2:SII33-38, 2002; Fiorentino, J. Am. Acad. Dermatol. 48:311-340, 2003.)Importantly, two vasculitis syndromes are associated with deposition ofimmune complexes: Henoch-Schonlein purpura is associated with depositionof IgA-containing immune complexes; and essential cryoglobulinemicvasculitis is associated with deposition of IgG/IgM immune complexes.(See Fiorentino, supra.)

The incidence of HCV infection in essential mixed cryoglobulinemiaranges from 40-100% in reported cases, depending on geography.Approximately 200 million worldwide are chronically infected with HCV,with 3.5 million new infections reported each year. (See Sy and Jamal,Int J. Med. Sci. 3:41-46, 2006.) The USA incidence and prevalence are30,000 new infections per year and 3.9 million with chronic infections.(See Sy and Jamal, supra.) Approximately 50-60% of patients with chronicHCV infections have cryoglobulins in their serum and overtcryoglobulinemic syndromes develop in about 5% of cases. (See Sansonnoet al., supra; Sansonno and Dammacco, supra.) Hepatitis B virus has beendescribed as an etiologic agent in 5% of patients with mixedcryoglobulinemia. (See Ferri et al. I, supra.)

The current therapies for cryoglobulinemia include low dose steroids formoderate disease and combinations of steroids, cyclophosphamide, orplasmapheresis are used for more severe forms of disease. Patients withactive HCV-mediated hepatitis are often treated with a combination ofinterferon-α and ribavirin.

The efficacy of the FcγRIA polypeptides of the invention can be testedin vivo in animal models of disease. A particularly suitable animalmodel for evaluating efficacy of soluble FcγRIA against immunecomplex-mediated disease, including cryoglobulinemia, are miceover-expressing thymic stromal lymphopoietin (TSLP), an interleukin-7(IL-7)-like cytokine with B-cell promoting properties. TSLP mice producelarge amounts of circulating cryoglobulins of mixed IgG-IgM composition.(See Taneda et al., Am. J. Pathol. 159:2355-2369, 2001.) Development ofmixed cryoglobulinemia in these animals is associated with systemicinflammatory disease involving kidneys, liver, lungs, spleen, and skin(see Taneda et al., supra) due to immune complex deposition in thesetissues. Kidney disease in these animals closely resembles humancryoglobulinemia glomerulonephritis as seen in patients with HCVinfection. A role for Fcγ receptors in the disease process was shown bythe exacerbation of renal injury with accelerated morbidity andmortality after deletion of the inhibitory receptor Fcγ receptor IIb.(See Muhlfeld et al., Am. J. Pathol. 163:1127-1136, 2003.) Treatment ofTSLP-transgenic mice with recombinant soluble FcγR in accordance withthe present invention is further described in Example 12, infra.

2. Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a complex, multi-organ (systemic)autoimmune disorder characterized by the production of pathogenicautoantibodies with subsequent deposition of immune complexes, whichresults in widespread tissue damage. Although the etiology of SLE isunknown, multiple genetic, environmental, and hormonal factors arethought to play a role in disease. (See Hahn, “Systemic LupusErythematosus” in Harrison's Principles of Internal Medicine (Kasper etal. eds., McGraw-Hill, New York 2005).) SLE is clinically characterizedby a waxing and waning course and by involvement of multiple organsincluding skin, kidneys, and central nervous system (Lupus: Molecularand Cellular Pathogenesis (Kammer and Tsokos eds., Human Press, N.J.,1st ed. 1999); Systemic Lupus Erythromatosus (Lahita ed., AcademicPress, Amsterdam, 3rd ed. 1999)). Thus, the disease displays a broadvariety of symptoms and clinical features, including systemic,cutaneous, renal, musculoskeletal, and hematologic.

The overall prevalence of SLE is about one in 2000, and about one in 700Caucasian women develops SLE during her life time. (Lahita, Curr. Opin.Rheumatol. 11:352-6, 1999). In the United States alone, over half amillion people have SLE, and most are women in their childbearing years(Hardin, J. Exp. Med. 185:1101-1111, 2003).

There is no single criteria to diagnose SLE. The American College ofRheumatology has developed 11 criteria to diagnose SLE, which span theclinical spectrum of SLE in aspects of skin, systemic, and laboratorytests. These criteria include malar rash, discoid rash, sensitivity tosun light, oral ulcers, arthritis, serositis, kidney and central nervoussystem inflammation, blood alterations, and the presence of antinuclearantibodies. A patient must meet four of these criteria in order to beclassified as a SLE patient. (Tan et al., Arthritis Rheumatol.25:1271-1277, 1982). SLE is usually confirmed by tests including, butnot limited to, blood tests to detect anti-nuclear antibodies; blood andurine tests to assess kidney function; complement tests to detect thepresence of low levels of complement that are often associated with SLE;a sedimentation rate (ESR) or C-reactive protein (CRP) to measureinflammation levels; X-rays to assess lung damage and EKGs to assessheart damage.

The standard therapy for SLE is administration of the steroidglucocorticoid, a general immune response inhibitor. It can be used torelieve symptoms; however, no cure for SLE is currently available. Lowdose p.o. prednisone at a level less than 0.5 mg/kg/day is usuallygiven. Unfortunately, this therapy is insufficient to keep patients inremission, and flaring of the disease is frequent Flares can becontrolled with high dose glucocorticoid via intravenous pulses at 30 mgmethylprednisolone/kg/day for 3 consecutive days. However, steroidtreatment at high dosage can present severe side effects for patients.

These standard treatments are generally nonspecific, are frequentlyassociated with serious side-effects and do not significantly affect theprogression of the disease or transition to life threatening kidneycomplications (lupus nephritis or LN). Consequently, there is along-felt need in the art to develop new methods for treating SLE.

3. Rheumatoid Arthritis

Rheumatoid arthritis (RA) is characterized by chronic joint inflammationthat typically leads to tissue damage and joint deformation. Althoughthe precise etiology is not clear, it is generally thought to be anautoimmune disease with roles played by immune complexes, a variety oflymphoid cell types (T-cells, B-cells, neutrophils, macrophages, anumber of pro-inflammatory cytokines such as TNF-α and IL-1β. (SeeHarrison's Principles of Internal Medicine (Kasper et al. eds.,McGraw-Hill, New York 2005); Olsen and Stein, N. Engl. J. Med.350:2167-2179, 2004.)

Rheumatoid arthritis is a systemic disease that affects the entire bodyand is one of the most common forms of arthritis. RA is immune-mediatedand is particularly characterized by inflammation and subsequent tissuedamage leading to severe disability and increased mortality. Inparticular, it is characterized by the inflammation of the membranelining the joint, which causes pain, stiffness, warmth, redness andswelling. Inflammatory cells release enzymes that may digest bone andcartilage. As a result of rheumatoid arthritis, the inflamed jointlining, the synovium, can invade and damage bone and cartilage leadingto joint deterioration and severe pain amongst other physiologiceffects. The involved joint can lose its shape and alignment, resultingin pain and loss of movement.

A variety of cytokines are produced locally in the rheumatoid joints.Numerous studies have demonstrated that IL-1 and TNF-α, two prototypicpro-inflammatory cytokines, play an important role in the mechanismsinvolved in synovial inflammation and in progressive joint destruction.Indeed, the administration of TNF-α and IL-1 inhibitors in patients withRA has led to a dramatic improvement of clinical and biological signs ofinflammation and a reduction of radiological signs of bone erosion andcartilage destruction. However, despite these encouraging results, asignificant percentage of patients do not respond to these agents,suggesting that other mediators are also involved in the pathophysiologyof arthritis (Gabay, Expert. Opin. Biol. Ther. 2:135-149, 2002). SinceRA is characterized by the presence of antibodies directed against TypeII collagen, a major extracellular matrix component of joint cartilage,these antibodies are thought to mediate the release of the inflammatorycytokines, such as those described above, through their interaction withsynoviocytes or other inflammatory cell types within the joint space.

Immunologic abnormalities that may be important in the pathogenesis ofRA also include immune complexes found in joint fluid cells and invasculitis. Contributing to these complexes are antibodies (such as RF)produced by plasma cells and T helper cells that infiltrate the synovialtissue and which can produce pro-inflammatory cytokines. Macrophages andtheir cytokines (e.g., TNF, GMCS-F) are also abundant in diseasedsynovium. Increased levels of adhesion molecules contribute toinflammatory cell emigration and retention in the synovial tissue.Increased macrophage-derived lining cells are also prominent, along withsome lymphocytes.

Established treatments of RA include disease modifying anti-rheumaticdrugs (DMARD) such as hydroxychloroquine, sulfasalazine, methotrexate,leflunomide, rituximab, infliximab, azathioprine, D-penicillamine, Gold(oral or intramuscular), minocycline and cyclosporine, coritcosteroidssuch as prednisone and non-steroidal anti-inflammatory drugs (NSAIDS).These treatments are generally nonspecific, are frequently associatedwith serious side-effects and do not significantly affect theprogression of joint destruction. Consequently, there is a long-feltneed in the art to develop new methods for treating RA.

The soluble FcγRIA polypeptides of the present invention could block theinteraction of the immune complexes with inflammatory cell types in thesynovium and prevent inflammation. Therefore, the FcγRIA polypeptides ofthe invention could serve as a valuable therapeutic to reduceinflammation in rheumatoid arthritis, and other arthritic diseases.

There are several animal models for rheumatoid arthritis known in theart. For example, in the collagen-induced arthritis (CIA) model, micedevelop chronic inflammatory arthritis that closely resembles humanrheumatoid arthritis. Since CIA shares similar immunological andpathological features with RA, this makes it an ideal model forscreening potential human anti-inflammatory compounds. The CIA model isa well-known model in mice that depends on both an immune response, andan inflammatory response, in order to occur. The immune responsecomprises the interaction of B-cells and CD4+ T-cells in response tocollagen, which is given as antigen, and leads to the production ofanti-collagen antibodies. The inflammatory phase is the result of tissueresponses from mediators of inflammation, as a consequence of some ofthese antibodies cross-reacting to the mouse's native collagen andactivating cellular Fc receptors and/or the complement cascade. Anadvantage in using the CIA model is that the basic mechanisms ofpathogenesis are known. The relevant T-cell and B-cell epitopes on typeII collagen have been identified, and various immunological (e.g.,delayed-type hypersensitivity and anti-collagen antibody) andinflammatory (e.g., cytokines, chemokines, and matrix-degrading enzymes)parameters relating to immune-mediated arthritis have been determined,and can thus be used to assess test compound efficacy in the CIA model(Wooley, Curr. Opin. Rheum. 3:407-20, 1999; Williams et al., Immunol.89:9784-788, 1992; Myers et al., Life Sci. 61:1861-78, 1997; and Wang etal., Immunol. 92:8955-959, 1995).

The administration of soluble hybrid FcγR polypeptides of the presentinvention to these CIA model mice can be used to evaluate the use ofsoluble FcγR to ameliorate symptoms and alter the course of disease. Byway of example and without limitation, the injection of 0.1 mg to 2.0 mgof a soluble hybrid FcγR polypeptide of the invention per mouse (one toseven times a week for up to but not limited to 4 weeks via s.c., i.p.,or i.m route of administration) can significantly reduce the diseasescore (paw score, incident of inflammation, or disease). Depending onthe initiation of administration (e.g., prior to or at the time ofcollagen immunization, or at any time point following the secondcollagen immunization, including those time points at which the diseasehas already progressed), antagonists of the present invention can beefficacious in preventing rheumatoid arthritis, as well as preventingits progression. As shown by studies described herein, administration ofa soluble FcγRIA polypeptide (residues 16-282 of SEQ ID NO:2)ameliorated symptoms and altered the course of disease in the mouse CIAmodel. (See Example 13, infra.)

Another model for immune complex mediated rheumatic disease is thecollagen antibody-induced model of arthritis in mice. (See Terato etal., J. Immunol. 48: 2103-2108, 1992.) Joint disease is induced in thismodel by the intravenous injection of a cocktail of four monoclonalantibodies, such as Arthrogen-CIA® from Chemicon, directed against TypeII collagen. Arthrogen-CIA® used for the induction of arthritis in miceis a mixture of four clones that recognize individual epitopes within an83 amino acid peptide within the CB11 domain of type II collagen(Chemicon International technical brochure). These epitopes are similarin type II collagen from human, mice, cow, chicken, monkey, and rat. Theantibodies localize to the joints of mice, where they form immunecomplexes with cartilage-specific type II collagen. The antigen-antibodyimmune complexes are thought to induce disease through their interactionwith Fc gamma receptors located on the surface of inflammatory celltypes within the joint. Typically, on day 0, 2-4 mg of Arthrogen-CIAcocktail is injected into mice by intravenous dosing. This is followedthree days later with an intraperitoneal injection of 50-100 μg of LPS.(See Terato et al., Autoimmunity 22:137-147, 1995.) Arthritis, evidentas red and swollen paws, develops with 1-2 days. In a typicalexperiment, the mice are treated on day 0 or day 3 by injection withsoluble FcγRIA (100-2000 g protein) dissolved in a suitable vehicle.Dosing with soluble hybrid FcγR can, for instance, be given every otherday starting on day 0 or day 3. The arthritis score for each animal canbe assessed everyday joint swelling and joint thickness. In a typicalexperiment, a soluble hybrid FcγR decreases the arthritis score.

4. Mixed Connective Tissue Disease

Mixed connective tissue disease is a rare disorder characterized byclinical features of SLE, systemic sclerosis, polymyositis ordermatomyositis, and RA and by very high titers of circulatingantinuclear antibody to a ribonucleoprotein (RNP) antigen. (SeeHarrison's Principles of Internal Medicine, supra; Kim and Grossman,Rheum. Dis. Clin. North Am. 31:549-565, 2005; Venables, Lupus15:132-137, 2006.) This antibody in high titer, now referred to asanti-UI RNP, has been a justification for considering MCTD as a distinctclinical entity. MCTD has been challenged as a distinct disorder bythose who consider it as a subset of SLE or scleroderma. Others preferto classify MCTD as an undifferentiated connective tissue disease. Handswelling, Raynaud's phenomenon, polyarthralgia, inflammatory myopathy,esophageal hypomotility, and pulmonary dysfunction are common. Diagnosisis by the combination of clinical features, antibodies to RNP, andabsence of antibodies specific for other autoimmune diseases. In somepatients, the disorder evolves into classic systemic sclerosis or SLE.

Raynaud's phenomenon may precede other manifestations by years.Frequently, the first manifestations resemble early SLE, scleroderma,polymyositis or dermatomyositis, or RA. Whatever the initialpresentation, limited disease tends to progress and become widespread,and the clinical pattern changes over time. The most frequent finding isswelling of the hands that eventually produces a sausagelike appearanceof the fingers. Skin findings include lupus or dermatomyositis-likerashes. Diffuse scleroderma-like skin changes and ischemic necrosis orulceration of the fingertips are much less frequent in MCTD. Almost allpatients have polyarthralgias, and 75% have frank arthritis. Often thearthritis is non-deforming, but erosive changes and deformities similarto those in RA may be present. Proximal muscle weakness with or withouttenderness is common. Renal disease occurs in about 10% and is oftenmild but occasionally causes morbidity or mortality. A trigeminalsensory neuropathy develops more frequently in MCTD than in otherconnective tissue diseases. Rheumatoid factors are frequently positive,and titers are often high. The ESR is frequently elevated.

MCTD is typically suspected when additional overlapping features arepresent in patients appearing to have SLE, scleroderma, polymyositis, orRA. Patients are first tested for antinuclear antibodies (ANA) andantibody to extractable nuclear antigen (ENA) and RNP antigen. Ifresults of these tests are compatible with MCTD (e.g., RNP antibodiesvery high), γ-globulin level, serum complement levels, rheumatoidfactors, anti Jo-1 (anti histidyl t-RNA synthetase), and antibodies tothe ribonuclease-resistant Smith (Sm) component of ENA, anddouble-stranded DNA are tested to exclude other possible diagnoses.Further workup depends on symptoms and signs; manifestations ofmyositis, renal involvement, or pulmonary involvement prompt tests ofthose organs (e.g., CPK, MRI, electromyogram, or muscle biopsy fordiagnosis of myositis).

The overall 10-yr survival rate is 80%, but prognosis depends largely onwhich manifestations predominate. Causes of death include pulmonaryhypertension, renal failure, MI, colonic perforation, disseminatedinfection, and cerebral hemorrhage. Some patients have sustainedremissions for many years without treatment.

Mixed connective tissue disease (MCTD) occurs worldwide and in allraces, with a peak incidence in the teens and 20s but MCTD is seen inchildren and the elderly. Women are predominantly affected. Theincidence and prevalence has not been clearly established. In moststudies, the number of patients with clinical and serologic features ofMCTD is ˜4-fold fewer than for SLE, suggesting an overall prevalence ofabout 10/100,000. (See Harrison's Principles of Internal Medicine,supra; Venables, supra.)

Current treatment for MCTD is similar to that for SLE, withcorticosteroids if disease is moderate or severe. Most patients withmoderate or severe disease respond to corticosteroids, particularly iftreated early. Mild disease is often controlled by salicylates, otherNSAIDs, anti-malarials, or sometimes low-dose corticosteroids. Severemajor organ involvement usually requires higher doses ofcorticosteroids.

5. Polyarteritis Nodosa-HBV Associated

Originally described by Kussmaul and Maier in 1866, classicpolyarteritis nodosa (PAN) is a multisystem disorder characterized by awide range of symptoms. (See Fiorentino, J. Am. Acad. Dermatol.48:311-340, 2003; Harrison's Principles of Internal Medicine, supra).PAN is a necrotizing vasculitis of small and medium-sized musculararteries with characteristic involvement of renal and visceral arteries.The lesions are segmental and tend to involve bifurcations andbranchings of arteries. In the acute stages of the disease, neutrophilsinfiltrate all layers of the vessel wall and perivascular areas,resulting in intimal proliferation and degeneration of the vessel wall.As the lesion progresses, mononuclear cells infiltrate the area,resulting in fibrinoid necrosis of the vessels with compromise of thelumen, thrombosis, infarction of the tissues supplied by the vessels,and hemorrhage. (See Fiorentino, supra.)

The presence of hepatitis B antigenemia is 10-30% of patients withsystemic vasculitis, particularly of the PAN type, together with theisolation of circulating immune complexes composed of hepatitis B viralantigens, suggest an immunologic role in pathogenesis of the disease.This notion is supported by findings of deposition of hepatitis Bantigen, IgM, and complement in blood vessel walls of patients with thisdisease. (See Fiorentino, supra.)

Patients usually present with fever, weight loss, arthralgias, andmalaise. Muscle wasting, abdominal pain, mononeutitis complex,hypertension, orchitis, and congestive heart failure are major symptomsdemonstrating vascular involvement of the respective organ systems. Ifsecondary to hepatitis B infection, the clinical findings are the same.The prognosis of untreated PAN is poor, with a reported 5-year survivalrate of 10-20%. (See Harrison's Principles of Internal Medicine, supra.)Death usually results from gastrointestinal complications, particularlybowel infarcts and perforation and by cardiovascular causes.

It is difficult to establish an accurate incidence of PAN becauseprevious reports have combined the incidence of PAN with microscopicpolyangiitis and related vasculitis disorders. The incidence of PAN hasbeen estimated, however, at 5-9 cases per million (see Fiorentino,supra) and it is estimated that ˜6% of cases are due to HBV infectionalthough a range of frequency from 10-54% has been reported (26, 27).

PAN patients are currently treated with steroids with or withoutcyclophosphamide. (See Fiorentino, supra.) For patients with HBV,antiviral treatment with interferon-α with or without vidarabine andlamivudine is effective when combined with plasma exchange. (SeeFiorentino, supra; Harrison's Principles of Internal Medicine, supra.)

6. Pemphigus Vulgaris

Pemphigus vulgaris (PV) is a blistering skin disease observed mostcommonly in elderly patients. The disease is characterized by the lossof cohesion between epidermal cells of the skin with the resultingformation of intraepidermal blisters. Direct immunofluorescence analysisof lesional or intact patient skin shows deposits of IgG on the surfaceof keratinocytes. Such deposits are derived from circulating IgGautoantibodies against desmogleins, transmembrane glycoproteins of theCa²⁺ dependent cadherin family. PV can be life threatening. The currentmainstay of treatment is systemic steroids, such as prednisone. Otherimmunosuppressants such as azathioprine or mycophenolate mofetil arealso used. (See Harrison's Principles of Internal Medicine, supra.)

7. Diseases Associated with Exogenous Antigens

Exogenous antigens produce a wide variety of immune complex diseasesincluding those caused by infection with viruses, bacteria, or parasitesas well as serum sickness caused by exposure to foreign proteins ordrugs. (See Jancar and Crespo, supra; Harrison's Principles of InternalMedicine, supra; Knowles and Shear, Dermatol. Clin. 25:245-253, 2007;Wolf et al., Clin. Dermatol. 23:171-181, 2005.) The bacterial infectionsassociated with tissue immune complex deposition include: streptococcal,staphylococcal and meningococcal; bartonellosis, borreliosis, leprosy,syphilis, and leptospirosis. The viral infections include: Hepatitis B(polyarteritis nodosa), Hepatitis C (cryoglobulinemia), HIV-relatedimmune complex nephropathy, human parvovirus B19 infection, CMVinfection, infectious mononucleosis, and dengue hemorrhagic fever. Theparasitic diseases include: Trypansoma, Plasmodium, Toxoplasma, andSchistosoma.

Currently, the most common serum sickness-like reactions are due toexposure to non-protein drugs. Drugs that have been implicated inserum-sickness-like reactions include: allopurinal, arsenicals andmercurial derivatives, barbiturates, bupropion, cephalosporins,furazolidone, gold salts, griseofulvin, hydralazine, infliximab,iodides, methyldopa, penicillins, phenyloin, piperazine, procainamide,streptokinase, and sulfonamides. Other causes of serum sickness likereactions include exposure to heterologous serum, allergen extracts,blood products, hormones, hymenoptera venom, and vaccines.

B. Other Diseases Involving Antibody Production

1. Idiopathic Thrombocytopenia Purpura (ITP)

Idiopathic thrombocytopenia purpura (ITP) is a systemic autoimmuneillness characterized by the presence of autoantibodies (IgG>IgM)directed against specific platelet membrane glycoproteins that resultsin platelet destruction (leading to thrombocytopenia), and which ischaracterized by extensive ecchymoses and hemorrhages from mucousmembranes, anemia, and extreme weakness. (See Harrison's Principles ofInternal Medicine, supra Cines and McMillan, Annu. Rev. Med. 56:425-442,2005; Stasi and Provan, Mayo Clin. Proc. 79:504-522, 2004.)

The platelet count becomes exceedingly low and spontaneous bleeding fromthe gums, gastrointestinal tract and nose can be seen. Purpura refers tothe purplish-looking areas of the skin and mucous membranes (such as thelining of the mouth) where bleeding has occurred as a result ofdecreased platelets. Physical examination may demonstrate enlargement ofthe spleen. A typical rash occurs due to microscopic hemorrhage of smallblood vessels in the skin. Platelet counts under 10,000 can lead tospontaneous hemorrhage into the brain, causing death. Also called immunethrombocytopenic purpura, purpura hemorrhagica, thrombocytopenicpurpura, Werlhof's disease. Although most cases are asymptomatic, verylow platelet counts can lead to a bleeding diathesis and purpura. Thereare two types of ITP, acute ITP that affects children (similar incidencein males and females) and chronic ITP affecting adults (more oftenwomen; 2.6 to 1; 72% of ITP patients older than 10 are women). Mostchildren recover without treatment. Peak prevalence in children is 2-4years, and in adults is 20-50 years; approximately 40% of all ITPpatients are younger than 10 years old.

Incidence of ITP: 4-8 per 100,000 children per year, 66 cases permillion adults, 50 cases per million children. New cases of chronicrefractory ITP comprise ˜10 cases per million per year. The number ofindividuals in the United States with ITP has been estimated to beapproximately 200,000. There are about 100 total new cases of ITP permillion people per year. Approximately half of the new cases are inchildren.

Mild ITP does not require treatment. When platelet counts fall under10,000 per microliter, or under 50,000 when hemorrhage occurs (e.g., inthe digestive tract or in a severe nosebleed) treatment is generallyinitiated with steroids. (See Cines and McMillan, supra.) Intravenousimmunoglobulin (IVIg) is used for life threatening cases. Later,so-called steroid-sparing agents (alternatively called DMARDs) may beused. When these strategies fail, splenectomy is often undertaken, asplatelets targeted for destruction will often meet their fate in thespleen. A relatively new strategy is treatment with anti-D, an agentusually used in mothers who have been sensitized to rhesus antigen by anRh+ baby. Other chemotherapeutic drugs such as vincristine, azathioprine(Imuran), Danazol, cyclophosphamide, and cyclosporine are prescribed forpatients only in the severe case where other treatments have not shownbenefit since these drugs have potentially harmful side effects. Mg,while effective, is expensive and the improvement is temporary(generally lasting less than a month). However, in the case of apre-splenectomy ITP patient with dangerously low platelet counts, and apoor response to other treatments, IVIg treatment can increase plateletcounts, making the splenectomy operation less dangerous.

2. Sjogren's Syndrome

Sjogren's syndrome (SS) is a chronic autoimmune disorder characterizedby lymphocytic infiltration of salivary and lacrimal glands, resultingin dry eyes and dry mouth. It is classified as either primary(autoimmune sicca (dryness) syndrome without underlying connectivetissue disorder) or secondary (autoimmune-mediated sicca syndrome in apatient with ongoing connective tissue disorder like RA, SLE or SSc).(See Harrison's Principles of Internal Medicine, supra.) Thefemale-to-male ratio for SS is 9:1, with a mean age at diagnosis of 60years. A model of pathogenesis postulates a virus or environmentalinsult in the appropriate genetic/hormonal background leads toepitheliitis in the salivary and lacrimal glands. The resultingmononuclear cell infiltrates (˜70% CD4+ T-cells, 25% CD8+ T-cells,20-30% B-cells) release cytokines (IFNγ), which in turn activatemacrophages that release proinflammatory cytokines: TNFα, IL-1β andIL-6. These cytokines then cause the release of MMPs from acinar cells,which degrade the basement membrane collagen. In time, the glandulartissue is replaced with scar tissue and fat. (See Harrison's Principlesof Internal Medicine, supra.)

In addition to dry mouth/eye symptoms, other symptoms can include:esophageal dysmotility, peripheral neuropathy arthralgia andfibromyalgia. 60% of patients present with autoantibodies (rheumatoidfactor, ANA, Ro/SS-A, La/SS-B) and suffer extreme fatigue. SS patientsare reported to have 44 times higher risk for developing lymphoma.

A variety of treatments have been used for SS including NSAIDs,steroids, hydroxychloroquine, and methotrexate. Several anti-cytokinetherapies are also in use but are not recommended as first-line therapy.These include: REMICADE, ENBREL, IFN-α, anti-IFN-γ, RITUXAN,cyclosporine, tacrolimus, and various topical ophthalmic preparations.

3. Antiphospholipid Antibody Syndrome

The antiphospholipid antibody syndrome is a common autoimmuneprothrombotic condition characterized by arterial and/or venousthrombosis and pregnancy morbidity associated with persistently positiveanti-cardiolipin antibodies and/or lupus anticoagulant. (See Harrison'sPrinciples of Internal Medicine, supra; Blume and Miller, Cutis78:409-415, 2006; Fischer et al., Semin. Nephrol. 27:35-46, 2007.)Recent evidence that some of these antibodies (IgG and IgM) are directlyagainst phospholipid binding proteins (B2-glycoprotein 1, prothrombin,protein C, protein S, TPA, and annexin V rather than the negativelycharged phospholipids themselves). APS can occur in association withother autoimmune disease, most commonly with SLE (secondary APS) or asan isolated disorder (primary APS).

APS affects any size of vessel and any organ of the body. Clinicalfeatures include peripheral venous and arterial thrombosis (deep veinthrombosis), fetal loss, skin disease, cardiac and pulmonarymanifestations, renal involvement, and neurological disorders (stroke).Thrombotic complications are the main cause of death in SLE patients.

APS is a common cause of acquired thrombophilia, with an estimated35,000 new cases of APS-associated venous thrombosis and 5000 new casesof arterial thrombosis in the U.S. per year. Patients with APSantibodies are 3-10 times more likely to have a recurrent thrombosisthan patients without these antibodies. In the U.S., about 2% of thegeneral population tests positive for anti-phospholipid antibodies(AAs), including lupus anticoagulant, anti-cardiolipin antibodies orboth. AAs were detected in 46% of patients with stroke or transientischemic attack under 50 years of age and in 21% of young survivors (<45years of age) of myocardial infarction. The prevalence of AAs inpatients with SLE is very high (30-50%). The prevalence of elevated AAsin dialysis patients varies between 0.7% and 69% in the publishedliterature. In patients with APS, the ratio of women to men is about 2to 1 for the primary form and 9 to 1 for cases associated with SLE.

The current therapy for patients who have APS but haven't experiencedthrombotic events or cutaneous changes is lifelong therapy with low doseaspirin. A patient with medium to high AA titers or thrombosis needsimmediate treatment with an anticoagulant such as heparin. Long-termtherapy is anticoagulation with warfarin. There is some clinical trialactivity of using cyclophosphamide in patients with life-threatening APSand using steroids to control APS-associated pregnancy loss. There isnot much precedent for using anti-B cell therapies for controlling thelevels of AAs.

4. Dermatomyositis

Dermatomyositis is a progressive condition characterized by symmetricproximal muscular weakness with elevated muscle enzyme levels and a skinrash, typically a purplish-red on the face, and edema of the eyelids andperiorbital tissue. (See Dalakas, Curr. Opin. Pharmacol. 1:300-306,2001; Dalakas, Nat. Clin. Pract. Rheumatol. 2:219-227, 2006.) Affectedmuscle tissue shows degeneration of fibers with a chronic inflammatoryreaction, occurs in children and adults, and in the latter may beassociated with visceral cancer. The cause of PM/DM is unknown. Althoughit rarely occurs in multiple family members, it may be linked to certainHLA types (e.g., DR3, DR5, or DR7). Infectious agents, includingviruses, and Toxoplasma and Borrelia species, have been suggested aspossible triggers of the disease. Several cases of drug-induced diseasehave been reported (e.g., hydroxyurea, penicillamine, statins,quinidine, and phenylbutazone). Immunological and humoral abnormalitiesare common (e.g., increased TNF-α in muscle, circulatingmyositis-specific autoAbs; abnormal T- and B-cell activity; familyhistory of other autoimmune diseases). B cells are the most abundantinflammatory cells at the perivascular sites.

Dermatomyositis is associated with skin problems (typically apurplish-red rash on the face, and edema of the eyelids and periorbitaltissue) and since articular, cardiac, pulmonary, and gastrointestinalmanifestations occur in up to 50% of the patients, the illness can beassociated with severe morbidity. It is often associated with otherconnective tissue autoimmune diseases, such as SLE, scleroderma, and RA.Unlike RA, arthritis associated specifically with DM/PM is not erosiveor deforming. Consistent with skin changes associated with otherautoimmune connective tissue diseases, such as SLE, there areperivascular inflammatory infiltrates in the skin. PM/DM is not usuallylife-threatening, but patients often develop residual weakness,disability, and reduced Quality of Life. PM/DM may cause death becauseof severe muscle weakness and/or cardiopulmonary involvement. Risk ofmalignancy is very high in patients with DM (incidence ratio=26) but notPM; the malignancy occurs more frequently in adults older than 60 years.Calcinosis (manifested by firm, yellow- or flesh-colored nodules) of theskin or muscle is unusual in adults but occurs in up to 40% of childrenor adolescents with DM; it is very debilitating. They can extrudethrough the surface of the skin, in which case secondary infection mayoccur.

The incidence of inflammatory myopathies (polymyositis alone, andpolymyositis and dermatomyositis combined has been estimated at 0.1 and1 per 100,000 people, respectively (no ethnic bias), and is apparentlyincreasing. Prevalence is 1 and 6 per 100,000 for PM alone and PM/DMcombined, respectively. Females are affected more than males (˜2:1).PM/DM can occur in people of any age. Two peak ages of onset exist. Inadults, the peak age of onset is approximately 50 years, and, inchildren, the peak age is approximately 5-10 years.

The mainstay of treatment is steroids. (See Dalakas, Jama 291:2367-2375,2004; Dalakas, Pharmacol. Ther. 102:177-193, 2004.) Immunosuppressanttherapy with methotrexate, azathioprine, and mycophenolate mofetil havealso been used. In refractory patients, IVIg has been used forshort-term therapy. Emerging therapies for this disorder includeRituxan. Although there is some concern that TNF antagonists mayincrease some of the risks associated with DM (infection, malignancy,induction of other autoimmune disease), REMICADE and ENBREL are beingstudied in ongoing clinical trials for this disorder.

5. Guillain-Barre Syndrome

Guillian-Barre syndrome is a severe post infectious neurologicaldisorder. The nerve damage observed in GBS patients is presumably causedby cross-reactive anti-ganglioside antibodies. The cellularimmunological background of the production of cross-reactive antibodiesin GBS is largely unknown. Some have hypothesized that a differentialresponse of dendritic cells to the most frequent antecedent infection inGBS, Campylobacter jejuni, results in enhanced B-cell proliferation anddifferentiation into autoreactive plasma cells. Host related factors aswell as pathogenic factors may be related to this. (See Harrison'sPrinciples of Internal Medicine, supra; Lewis, Neurol. Clin. 25:71-87,2007; Said, Neurol. Clin. 25:115-137, 2007; Yuki, Muscle Nerve35:691-711, 2007.)

GBS is a devastating disorder with a mortality of 5-15%. IVIg are thefirst choice treatment for these patients. (See Harrison's Principles ofInternal Medicine, supra). Still, about 50% of patients are unable towalk independently after 6 months. GBS consists of at least foursubtypes of acute peripheral neuropathy. The histological appearance ofthe acute inflammatory demyelinating polyradiculoneuropathy (AIDP)subtype resembles experimental autoimmune neuritis, which ispredominantly caused by T cells directed against peptides from themyelin proteins P0, P2, and PMP22. The role of T-cell-mediated immunityin AIDP remains unclear and there is evidence for the involvement ofantibodies and complement. Strong evidence now exists that axonalsubtypes of GBS, acute motor axonal neuropathy (AMAN), and acute motorand sensory axonal neuropathy (AMSAN), are caused by antibodies togangliosides on the axolemma that target macrophages to invade the axonat the node of Ranvier. About a quarter of patients with GBS have had arecent Campylobacter jejuni infection, and axonal forms of the diseaseare especially common in these people. The lipo-oligosaccharide from theC jejuni bacterial wall contains ganglioside-like structures and itsinjection into rabbits induces a neuropathy that resembles acute motoraxonal neuropathy. Antibodies to GM1, GM1b, GD1a, and GalNac-GD1a are inparticular implicated in acute motor axonal neuropathy and, with theexception of GalNacGD1a, in acute motor and sensory axonal neuropathy.The Fisher's syndrome subtype is especially associated with antibodiesto GQ1b, and similar cross-reactivity with ganglioside structures in thewall of C jejuni has been discovered. Anti-GQ1b antibodies have beenshown to damage the motor nerve terminal in vitro by acomplement-mediated mechanism.

GBS is a rare disorder and affects men and women equally in the US (NIH,The National Women's Health Centre, 2004). GBS affects 1 person per100,000 population in the US (NIH, The National Women's Health Centre,2004). The U.S. prevalence of all chronic inflammatory demyelinatingpolyneuropathies (CIDP), including GBS is about −1 to 7.7 per 100,000(2,000-15,000 cases in U.S.). However, this is probably anunderestimate, assuming that CIDP constitute 5% of all neuropathies (10million cases), then one might expect there are actually ˜300,000(active)-500,000 cases in total.

IVIg and plasmapheresis are currently used as therapy for GBS. Since GBSis an autoimmune neuropathy, it is anticipated that therapies directedtowards T-cells, B-cells, and/or complement may be useful in thesediseases.

6. Goodpasture's Syndrome

The term “Goodpasture's syndrome” (GPS) is an eponym derived from areport in 1919 by Ernest Goodpasture, who described the clinicalsyndrome of pulmonary hemorrhage associated with influenza infection andthe histologic finding of acute crescentic glomerulonephritis. Over theyears, the terminology has been used in different ways by differentpersons, some including all causes of pulmonary hemorrhage with renaldysfunction as GPS. Others limited the term GPS to patients withpulmonary hemorrhage associated with anti-glomerular basement membrane(anti-GBM) antibodies, as opposed to glomerulonephritis with anti-GBMantibodies but without pulmonary hemorrhage. Yet others espouse theconcept of anti-type-IV collagen disease rather than GPS.

The sine qua non for the diagnosis of GPS is demonstration of boundanti-GBM antibodies in the glomeruli of the kidneys. Circulatinganti-GBM antibodies are present in more than 90% of patients withanti-GBM disease. The clinical course of untreated, and even treated,GPS is bleak; this disease is associated with an extremely poorprognosis.

GPS is a rare disease, having an incidence of about 0.1 case per millionpeople. The disease is more common in whites than in African Americansand may be more common in certain other racial groups, such as theMaoris in New Zealand. GPS can present year round, but its incidenceappears to increase in the spring and early summer.

The current therapies for GPS include steroids, immunosuppressants, andplasma exchange. Since the renal pathology appears to be due to theaccumulation of anti-GBM antibodies in kidney glomeruli, B-cell directedtherapies may be useful in this disease.

From the foregoing, it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention isfurther illustrated by the following non-limiting examples and is notlimited except as by the appended claims.

Example 1 Construction of Mammalian Soluble FcγRIA Expression Constructsthat Express FcγRIA-CEE, FcγRIA-CIIS, and FcγRIA-CFLAG Tagged Proteins

An expression construct containing the extracellular domain of humanFcγRIA with a C-terminal tag, either Glu-Glu (CEE), six His (CHIS), orFLAG (CFLAG), is constructed via PCR and homologous recombination usinga DNA fragment encoding FcγRIA (SEQ ID NO:14) and the expression vectorpZMP20.

The PCR fragment encoding FcγRIA-CEE contains a 5′ overlap with thepZMP20 vector sequence in the 5′ non-translated region, an FcγRIAextracellular domain coding region portion of SEQ ID NO:14 (nucleotides1-846), the Glu-Glu tag (Glu Glu Tyr Met Pro Met Glu; SEQ ID NO:15)coding sequence, and a 3′ overlap with the pZMP20 vector in thepoliovirus internal ribosome entry site region. The PCR amplificationreaction uses the 5′ oligonucleotide “100”(ACAGGTGTCCAGGGAATTCATATAGGCCGGCCACCATGTGGTTCTTGACAACTCTG; SEQ IDNO:16), the 3′ oligonucleotide “200”(CAACCCCAGAGCTGTTTTAAGGCGCGCCTCTAGATTATTCCATGGGCATGTATTCTTCCACTTGAAGCTCCAACTCAGG; SEQ ID NO:17), and apreviously generated DNA clone of FcγRIA as the template (SEQ ID NO:14).

The PCR amplification reaction condition is as follows: 1 cycle, 94° C.,5 minutes; 35 cycles, 94° C., 1 minute, followed by 55° C., 2 minutes,followed by 72° C., 3 minutes; 1 cycle, 72° C., 10 minutes. The PCRreaction mixture is run on a 1% agarose gel and the DNA fragmentcorresponding to the expected size is extracted from the gel using aQIAquick™ Gel Extraction Kit (Qiagen, Cat. No. 28704).

Plasmid pZMP20 is a mammalian expression vector containing an expressioncassette having the chimeric CMV enhancer/MPSV promoter, a BglII sitefor linearization prior to yeast recombination, an internal ribosomeentry element from poliovirus, the extracellular domain of CD8 truncatedat the C-terminal end of the transmembrane domain; an E. coli origin ofreplication; a mammalian selectable marker expression unit comprising anSV40 promoter, enhancer and origin of replication, a DHFR gene, and theSV40 terminator; and URA3 and CEN-ARS sequences required for selectionand replication in S. cerevisiae.

The plasmid pZMP20 is digested with BglII prior to recombination inyeast with the gel extracted FcγRIA-CEE PCR fragment. One hundred μl ofcompetent yeast (S. cerevisiae) cells are combined with 10 μl of theFcγRIA-CEE insert DNA and 100 ng of BglII digested pZMP20 vector, andthe mix is transferred to a 0.2 cm electroporation cuvette. Theyeast/DNA mixture is electropulsed using power supply (BioRadLaboratories, Hercules, Calif.) settings of 0.75 kV (5 kV/cm), ∞ ohms,and 25 μF. Six hundred μl of 1.2 M sorbitol is added to the cuvette, andthe yeast is plated in 100 μl and 300 μl aliquots onto two URA-D platesand incubated at 30° C. After about 72 hours, the Ura⁺ yeasttransformants from a single plate are resuspended in 1 ml H₂O and spunbriefly to pellet the yeast cells. The cell pellet is resuspended in 0.5ml of lysis buffer (2% Triton X-100, 1% SDS, 100 mM NaCl, 10 mM Tris, pH8.0, 1 mM EDTA). The five hundred μl of the lysis mixture is added to anEppendorf tube containing 250 μl acid-washed glass beads and 300 μlphenol-chloroform, is vortexed for 3 minutes, and spun for 5 minutes inan Eppendorf centrifuge at maximum speed. Three hundred μl of theaqueous phase is transferred to a fresh tube, and the DNA isprecipitated with 600 μl ethanol, followed by centrifugation for 30minutes at maximum speed. The tube is decanted and the pellet is washedwith 1 mL of 70% ethanol. The tube is decanted and the DNA pellet isresuspended in 30 μl 10 mM Tris, pH 8.0, 1 mM EDTA.

Transformation of electrocompetent E. coli host cells (DH12S) is doneusing 5 μl of the yeast DNA preparation and 50 μl of E. coli cells. Thecells are electropulsed at 2.0 kV, 25 μF, and 400 ohms. Followingelectroporation, 1 ml SOC (2% Bacto™ Tryptone (Difco, Detroit, Mich.),0.5% yeast extract (Difco), 10 mM NaCl, 2.5 mM KCl, 10 mM MgCl₂, 10 mMMgSO₄, 20 mM glucose) is added and then the cells are plated in 50 μland 200 μl aliquots on two LB AMP plates (LB broth (Lennox), 1.8% Bacto™Agar (Difco), 100 mg/L Ampicillin).

The inserts of three DNA clones for the construct are subjected tosequence analysis and one clone containing the correct sequence isselected. Large-scale plasmid DNA is isolated using a commerciallyavailable kit (QIAGEN Plasmid Mega Kit, Qiagen, Valencia, Calif.)according to manufacturer's instructions.

The same process is used to prepare the FcγRIA with a C-terminal histag, composed of Gly Ser Gly Gly His His His His His His (SEQ ID NO:18)(FcγRIA-CHIS) or the C-terminal FLAG tag, composed of Gly Ser Asp TyrLys Asp Asp Asp Asp Lys (SEQ ID NO:19) (FcγRIA-CFLAG). To prepare theseconstructs, instead of the 3′ oligonucleotide “200”, the 3′oligonucleotide “300”(CAACCCCAGAGCTGTTTTAAGGCGCGCCTCTAGATTAGTGATGGTGATGGTGATGTCCACCAGATCCCACTTGAAGCTCCAACTCAGG; SEQ ID NO:20) is used to generateFcγRIA-CHIS or the 3′ oligonucleotide “400”(CAACCCCAGAGCTGTITAAGGCGCGCCTCTAGATTACTTATCATCATCATCCTTATAATCGGATCCCACTTGAAGCTCCAACTCAGG; SEQ ID NO:21) isused to generate FcγRIA-CFLAG.

Example 2 Transfection and Expression of Soluble FcγRIA ReceptorExpression Constructs that Express the FcγRIA-CEE, FcγRIA-CHIS, andFcγRIA-CFLAG C-Terminal Tagged Proteins

Three sets of 200 μg of each of the soluble FcγRIA tagged expressionconstructs are separately digested with 200 units of PvuI at 37° C. forthree hours, precipitated with isopropyl alcohol, and centrifuged in a1.5 mL microfuge tube. The supernatant is decanted off the pellet, andthe pellet is washed with 1 mL of 70% ethanol and allowed to incubatefor 5 minutes at room temperature. The tube is spun in a microfuge for10 minutes at 14,000 RPM and the supernatant is decanted off the pellet.The pellet is then resuspended in 750 μl of CHO cell tissue culturemedium in a sterile environment, allowed to incubate at 60° C. for 30minutes, and is allowed to cool to room temperature. Approximately 5×10⁶CHO cells are pelleted in each of three tubes and are resuspended usingthe DNA-medium solution. The DNA/cell mixtures are placed in a 0.4 cmgap cuvette and electroporated using the following parameters; 950 μF,high capacitance, at 300 V. The contents of the cuvettes are thenremoved, pooled, and diluted to 25 mL with CHO cell tissue culturemedium and placed in a 125 mL shake flask. The flask is placed in anincubator on a shaker at 37° C., 6% CO₂ with shaking at 120 RPM.

The CHO cells are subjected to nutrient selection followed by stepamplification to 200 nM methotrexate (MTX), and then to 1 μM MTX. Taggedprotein expression is confirmed by Western blot, and the CHO cell poolis scaled-up for harvests for protein purification.

Example 3 Purification of FcγRIA-CH6

An expression construct containing the extracellular domain of humanFcγRIA with a C-terminal six His (CHIS) tag was constructed as describedin Example 1, supra. This construct was transfected into and expressedin CHO cells as described in Example 2, supra. The encoded His-taggedFcγRIA, referred to in the Examples above as “FcγRIA-CHIS,” is alsoreferred to herein as “FcγRIA-CH6” or “pFCGR1A CH6.” The nucleotidecoding sequence for FcγRIA-CH6 is shown in SEQ ID NO:22, and thecorresponding FcγRIA-CH6 amino acid sequence is shown in SEQ ID NO:23.The expressed FcγRIA-CH6 was purified as described below. FcγRIA-CH6 waspurified from CHO conditioned media by a combination of Ni IMAC capture,chromatography on Q Sepharose, and size exclusion chromatography onSuperdex 200. Ni IMAC capture: CHO conditioned media was sterilefiltered (0.22 μm) and concentrated 10× using a peristaltic pump systemequipped with 10 kD MWCO 0.1 m² membrane. Concentrated media was bufferexchanged with at least 5 CV of 50 mM NaPO₄, 500 mM NaCl pH 7.5 and wasadjusted to a final concentration of 25 mM imidazole. The pH wasadjusted to 7.5 using either concentrated NaOH or HC, if necessary. TheHis-tagged FcγRIA protein was captured using IMAC binding to Ni-NTA HisBind Superflow resin. Prior to application of media, the resin wasequilibrated in 50 mM NaPO₄, 500 mM NaCl, 25 mM Imidazole pH 7.5.Binding was allowed to occur overnight at 4° C. in either batch modeusing an appropriately sized roller bottle or column mode using achromatography station. Following the load, the resin was washed with atleast 10 CV of 50 mM NaPO₄, 500 mM NaCl, and 25 mM Imidazole pH 7.5.Elution of bound protein was accomplished using either a gradient orsteps of increasing imidazole concentration in 50 mM NaPO₄, 500 mM NaClpH 7.5, with 500 mM Imidazole being the end point in the elution.Fractions were collected and analyzed by western blotting, SDS-PAGE, andRP-HPLC and fractions containing FcγRIA-CH6 were combined.

Q Sepharose Passive Chromatography: The IMAC pool containing FcγRIA-CH6was buffer exchanged with 15 CV into 50 mM NaPO₄, 150 mM NaCl pH 7.5through the use of a Labscale TFF system equipped with 3×10 kD MWCO 0.1cm² membranes. A 1.0 mL sample of Q Sepharose resin per 7.5 mg ofFcγRIA-CH6 was charged using at least 10 CV of 50 mM NaPO₄, 2M NaCl pH7.5, and then equilibrated with 10 CV of 50 mM NaPO₄, 150 mM NaCl pH7.5. Resin and the adjusted IMAC pool were combined and incubatedovernight at 4° C. with gentle agitation. The slurry was transferred toa gravity flow column, the flow-through was collected and the column waswashed with at least 5 CV of equilibration buffer. The flow-through andwash fractions were combined and assessed for the presence of FcγRIA-CH6by RP-HPLC and SDS-PAGE.

Size Exclusion Chromatography: The Q Sepharose flow-through + washfraction was concentrated at least 10- to 20-fold using either the TFFlabscale system equipped with a 10 kD MWCO 0.1 cm² membrane, a stirredcell system equipped with a YM30 membrane of appropriate diameter, or a30 kD MWCO Ultracel centrifugal membrane, depending on the fractionvolume. The concentrated FcγRIA-CH6 fraction was injected over aSuperdex 200 column of appropriate size for the amount of volume andmass injected. The column was equilibrated in formulation buffer whichcontained. 50 mM NaPO₄, 109 mM NaCl, pH 7.3 or 35 mM NaPO₄, 120 mM NaClpH 7.2. The column was eluted isocratically at a flow rate no greaterthan 45 cm/hr, fractions were collected and analyzed for the presence ofFcγRIA-CH6 by SDS-PAGE and RP-HPLC. Fractions containing FcγRIA-CH6 werecombined and concentrated to the desired concentration using a stirredcell apparatus equipped with a YM30 membrane (30 kD MWCO). The finalFcγRIA-CH6 concentrate was filtered through a 0.22 um sterile filter andstored at −80° C. until use.

Example 4 Construction, Expression, and Purification of SolubleFcγRIIA-CH6 and FcγRIIIA-CH6

In addition to construction, expression, and purification of a solublemonomeric form of FcγRIA with a C-terminal His6 tag as described abovein Examples 1, 2, and 3, supra, soluble monomeric forms of FcγRIIA andFcγRIIIA were also generated using similar methods.

Briefly, expression constructs encoding soluble monomeric forms of theFcγRIIA and FcγRIIIA were generated using DNA sequences encoding theirnative signal sequence, their extracellular domain, and a C-terminalHis6 tag (GSGGHHHHHH; SEQ ID NO:18). The DNA sequence encoded aminoacids 1-212 for FcγRIIA (amino acids 1-212 of SEQ ID NO:25) and 1-195for FcγRIIA (amino acids 1-195 of SEQ ID NO:27). Receptors were purifiedfrom supernatants derived from Chinese hamster ovary (CHO) DXB-11 cells(Larry Chasin, Columbia University, New York, N.Y.). CHO-conditionedmedia were sterile filtered, concentrated, and buffer exchanged into 50mM NaPO₄, 500 mM NaCl, 25 mM imidazole, pH 7.5 (Buffer A). TheHis-tagged FcγR proteins (FcγRIIA-CH6 and FcγRIIIA-CH6) were capturedusing Ni-NTA His Bind Superflow resin (Novagen, Madison, Wis.)equilibrated in Buffer A. Elution of bound protein was accomplishedusing a gradient of imidazole (0-500 mM) in 50 mM NaPO₄, 500 mM NaCl, pH7.5. Fractions were analyzed for soluble FcγR by SDS-PAGE and Westernblotting (anti-6× Histidine HRP mouse IgG1, R & D Systems, Minneapolis,Minn.).

The Ni-NTA fractions containing soluble FcγR were buffer-exchanged into50 mM NaPO₄, 150 mM NaCl, pH 7.5 (Buffer B) and incubated with QSepharose 4FF resin (GE Healthcare, Uppsala, Sweden) that waspre-equilibrated in Buffer B overnight at 4° C. The slurry wastransferred to a gravity flow column, the flow-through and washfractions were combined and assessed for the presence of soluble FcγR asdescribed above. The combined fractions were concentrated and injectedonto a Superdex 200 Hiload (GE Healthcare, Uppsala, Sweden) columnequilibrated in 50 mM NaPO₄, 109 mM NaCl, pH 7.3 (Buffer C). The columnwas eluted in Buffer C and fractions containing soluble FcγR werecombined, concentrated, sterile-filtered, and stored at −80° C.FcγRIIA-CH6 and FcγRIIIA-CH6 were analyzed by SDS-PAGE, Westernblotting, N-terminal sequencing, and size exclusion multi-angle lightscattering. Endotoxin levels were <1.0 endotoxin units/mL for eachreceptor preparation formulated at ˜20 mg/mL.

The nucleotide coding sequences for FcγRIIA-CH6 and FcγRIIIA-CH6 areshown in SEQ ID NO:24 and SEQ ID NO:26, respectively. The encodedpolypeptide sequences for FcγRIIA-CH6 and FcγRIIIA-CH6 and shown in SEQID NO:25 and SEQ ID NO:27, respectively. N-terminal sequence analysisshowed Gln-34 as the start site for mature FcγRIIA-CH6 and both Met-18and Glu-21 as the start site for mature FcγRIIIA-CH6. Accordingly, themature form the of FcγRIIA-CH6 polypeptide, without the signal sequence,corresponds to amino acid residues 34-222 of SEQ ID NO:25, while themature forms of FcγRIIIA-CH6 correspond to amino acid residues 18-205and 21-205 of SEQ ID NO:27.

Example 5 Binding of Soluble His-Tagged FcγR (FcγRIA-CH6, FcγRIIA-CH6,and FcγRIIIA-CH6) to Immobilized Human IgG1

Measurements were performed using a Biacore 3000 instrument (Piscataway,N.J.). Activation of the sensor chip surface and covalent immobilizationof the IgG1 antibody (Lambda from human myeloma plasma, Sigma-Aldrich,St Louis, Mo.) was performed using 0.2 MN-ethyl-N′-(3-diethylamino-propyl) carbodiimide and 0.05 MN-hydroxysuccinamide and the Biacore Control Software. The human IgG1antibody, diluted to 11 μg/mL in 10 mM sodium acetate, pH 5.0, wasimmobilized to prepare the specific binding flow cell, and a second flowcell was activated, but not exposed to IgG1 to prepare the referenceflow cell. The un-reacted ester sites on both the specific binding andreference flow cells were blocked with 1 M ethanolamine hydrochloride.

For kinetic analysis of soluble FcγRIA binding, the IgG1 antibody wasimmobilized at a level of 458 resonance units (RU). FcγRIA-CH6 wasinjected over both the active and reference flow cells in series. Forkinetic analysis of FcγRIA-CH6 binding, a concentration range of 0.16 to10.3×10⁻⁹ M of FcγRIA-CH6 in HBS-EP (Biacore) assay buffer (10 mM Hepes,pH 7.4, 0.15M NaCl, 3.5 mM EDTA, 0.005% polysorbate 20) was used.FcγRIA-CH6 was injected at a flow rate of 40 μL/min for 3 minutes.Subsequently, the FcγRIA-CH6 solution was switched to HBS-EP buffer anddissociation was measured for 3 minutes. Each FcγRIA-CH6 concentrationwas tested in duplicate using a random sequence. Each measurement wasfollowed by a single 30 second injection of 10 mM glycine-HCl, pH 1.8 at50 μL/min to regenerate the IgG1 surface.

For equilibrium analyses of soluble FcγRIIA and FcγRIIIA binding, theIgG1 antibody was immobilized at a level of 1013 RU. A concentrationrange of 0.03−24×10⁻⁶ M of soluble FcγR was used. Each soluble FcγR(FcγRIIA-CH6 and FcγRIIIA-CH6) was injected at a flow rate of 10 μL/minfor 1 minute. The dissociation time for each FcγR was 5 minutes. EachFcγRIIA-CH6 and FcγRIIA-CH6 concentration was tested in duplicate usinga random sequence. Each measurement was followed by a single 30 secondinjection of HBS-EP at 30 μL/min to regenerate the IgG1 surface.

Binding curves for all three soluble FcγRs were processed by subtractionof the reference surface curve from the specific binding surface curve,as well as subtraction of a buffer-injection curve. The processedbinding curves were globally fitted to a 1:1 binding model and theresulting kinetic and equilibrium constants were evaluated using Biacoresoftware.

The soluble FcγRs bound to immobilized human IgG1 in a manner that wasbest-fit by a 1:1 binding interaction. The IgG1 exhibited some loss ofbinding activity upon covalent immobilization and the activity of thesurface ranged from 26-81% of the theoretical maximum. The associationand dissociation phases of FcγRIA-CH6 binding to IgG1 were measurableover a time period of >200 seconds, allowing kinetic analysis of thebinding curves. FcγRIA-CH6 bound to IgG1 with association (k_(a)) anddissociation (k_(d)) rate constants of 2.8×10⁶ M⁻¹s⁻¹ and 4.6×10⁻⁴ s⁻¹,respectively, yielding an equilibrium dissociation constant (K_(D)) of1.7×10⁻¹⁰ M. The association/dissociation rates for FcγRIIA-CH6 andFcγRIIIA-CH6 were too fast to measure accurately, so the equilibriumdissociation constants were determined at steady state. Binding ofFcγRIIIA-CH6 and FcγRIIA-CH6 to IgG1 was saturable and of low affinitywith estimated K_(D)s of 0.63×10⁻⁶ M and 1.9×10⁻⁶ M, respectively. Eachsoluble FcγR bound to immobilized rabbit anti-OVA IgG with rates andaffinities similar to that observed with human IgG1.

Example 6 Construction of Mammalian Soluble FcγRIA Expression Constructsthat Expresses Soluble Monomeric Untagged FcγRIA Protein

Two expression constructs containing the extracellular domain of humanFcγRIA were constructed via PCR and homologous recombination using a DNAfragment encoding the extracellular domain of a short version FcγRIA(amino acids 1-282 of SEQ ID NO:2) and a long version FcγRIA (additionalten amino acids at the C-terminus) (amino acids 1-292 of SEQ ID NO:2)and the expression vector pZMP31.

PCR fragments encoding the short and long version of FcγRIA wereconstructed to contain a 5′ overlap with the pZMP31 vector sequence inthe 5′ non-translated region, the FcγRIA extracellular domain codingregion corresponding to SEQ ID NO:2 amino acid residues 1-282 or 1-292,respectively, and a 3′ overlap with the pZMP31 vector in the poliovirusinternal ribosome entry site region. The PCR amplification reaction forboth the short and long version used the 5′ oligonucleotide “zc57709”(ACTTTOCCTTTCTCTCCACAGGTGTCCAGGGAATTCATATAGGCCGGCCACCATGTGGTTCTTGACAACT; SEQ ID NO:28). The 3′ oligonucleotide“zc57710” (TGGGGTGGGTACAACCCCAGAGCTGTTTAAGGCGCGCCTTTAGCCAAGCACTTGAAGCTCCA; SEQ ID NO:29) was used for the short version and the 3′oligonucleotide “zc57712”(TGGGGTGGGTACAACCCCAGAGCTGTTTrAAGGCGCGCCTTTAATGAAACCAGACAGGA GT; SEQ IDNO:30) was used for the long version. The FcγRIA template was from apreviously generated cDNA of FcγRIA.

The PCR amplification reaction conditions were as follows: 1 cycle, 95°C., 2 minutes; 30 cycles, 95° C., 15 seconds, followed by 55° C., 30seconds, followed by 68° C., 1 minute. The PCR reaction mixture was runon a 1% agarose gel and the DNA fragment corresponding to the expectedsize was extracted from the gel using a GE Healthcare illustra GFX™ PCRDNA and Gel Band Purification Kit.

Plasmid pZMP31 is a mammalian expression vector containing an expressioncassette having the chimeric CMV enhancer/MPSV promoter, an EcoRI sitefor linearization prior to yeast recombination, an internal ribosomeentry element from poliovirus; an E. coli origin of replication andampicillin selectable marker, a mammalian selectable marker expressionunit comprising an SV40 promoter, enhancer and origin of replication, aDHFR gene, and the SV40 terminator, and URA3 and CEN-ARS sequencesrequired for selection and replication in S. cerevisiae.

The plasmid pZMP31 was digested with EcoRI prior to recombination inyeast with each of the gel extracted FcγRIA PCR fragments of the shortand long version. One hundred μl of competent yeast (S. cerevisiae)cells were combined with 20 μl of the FcγRIA short or long insert DNAand ˜100 ng of EcoRI digested pZMP31 vector. The mix was transferred toa 0.2 cm electroporation cuvette. The yeast/DNA mixture waselectropulsed using power supply (BioRad Laboratories, Hercules, Calif.)settings of 0.75 kV (5 kV/cm), ∞ ohms, and 25 μF. Six hundred μl of 1.2M sorbitol was added to the cuvette, and the yeast was plated in two 300μl aliquots onto two URA-D plates and incubated at 30° C. After about 72hours, the Ura+ yeast transformants from a single plate were resuspendedin 800 μl H₂O and spun briefly to pellet the yeast cells. The cellpellet was resuspended in 0.5 ml of lysis buffer (2% Triton X-100, 1%SDS, 100 mM NaCl, 10 mM Tris, pH 8.0, 1 mM EDTA). The five hundred μl ofthe lysis mixture was added to an Eppendorf tube containing 250 μlacid-washed glass beads and 300 μl phenol-chloroform, was vortexed for 3minutes, and spun for 5 minutes in an Eppendorf centrifuge at maximumspeed. Three hundred μl of the aqueous phase was transferred to a freshtube, and the DNA was precipitated with 600 μl ethanol, followed bycentrifugation for 10 minutes at maximum speed. The tube was decantedand the pellet was washed with 1 mL of 70% ethanol, followed bycentrifugation for 10 minutes at maximum speed. The tube was decantedand the DNA pellet was resuspended in 10 μl H₂O.

Transformation of electrocompetent E. coli host cells (DH10B) was doneusing 1 μl of the yeast DNA preparation and 20 μl of E. coli cells. Thecells were electropulsed at 2.0 kV, 25 μF, and 400 ohms. Followingelectroporation, 600 μl SOC (2% Bacto™ Tryptone (Difco, Detroit, Mich.),0.5% yeast extract (Difco), 10 mM NaCl, 2.5 mM KCl, 10 mM MgCl₂, 10 mMMgSO₄, 20 mM glucose) was added and the cells were plated in 50 μl and550 μl aliquots on two LB AMP plates (LB broth (Lennox), 1.8% Bacto™Agar (Difco), 100 mg/L Ampicillin).

The colonies were screened via colony PCR and the inserts of five DNAclones from each construct were subjected to sequence analysis. Oneclone containing the correct sequence was selected. DNA sequencing wasperformed using ABI PRISM BigDye Terminator v3.1 Cycle Sequencing Kit(Applied Biosystems, Foster City, Calif.). Sequencing reactions werepurified using EdgeBioSystems Preforma Centriflex Gel FiltrationCartridges (Gaithersburg, Md.) and run on an Applied Biosystems 3730 DNAAnalyzer (Applied Biosystems, Foster City, Calif.). Resultant sequencedata was assembled and edited using Sequencher v4.6 software (GeneCodesCorporation, Ann Arbor, Mich.). One clone containing the correctsequence was selected and large-scale plasmid DNA was isolated using acommercially available kit (QIAGEN Plasmid Mega Kit, Qiagen, Valencia,Calif.) according to manufacturer's instructions.

The sequences of the short and long versions of the insert DNA are shownin SEQ ID NO:31 and SEQ ID NO:33, respectively. The correspondingencoded amino acid sequences for the short and long versions of untaggedFcγRIA are shown in SEQ ID NO:32 and SEQ ID NO:34, respectively. Thesignal sequence for FcγRIA corresponds to amino acids 1-15 of SEQ IDNO:2 (residues 1-15 of SEQ ID NOs 40 and 42), thereby yielding a startsite for the mature untagged FcγRIA proteins at position 16 of SEQ IDNOs 32 and 34.

Example 7 Transfection and Expression of Soluble FcγRIA ReceptorExpression Constructs that Express Untagged FcγRIA Protein

Two hundred μg of the soluble FcγRIA short and long version expressionconstructs were digested with 200 units of BstB1 at 37° C. for eighteenhours (overnight), washed with phenol/chloroform/isoamyl alcohol,precipitated with ethanol, and centrifuged in a 1.5 mL microfuge tube.The supernatant was decanted off the pellet, and the pellet was washedwith 1 mL of 70% ethanol and allowed to incubate for 5 minutes at roomtemperature. The tube was spun in a microfuge for 10 minutes at 14,000RPM and the supernatant was decanted off the pellet. The pellet was thenresuspended in 200 μl of CHO cell tissue culture medium in a sterileenvironment, allowed to incubate at 37° C. for 30 minutes. Approximately1×10⁷ CHO cells were pelleted and were resuspended using the DNA-mediumsolution. The DNA/cell mixtures were placed in a 0.4 cm gap cuvette andelectroporated using the following parameters; 950 μF, high capacitance,at 300 V. The contents of the cuvettes were then removed, pooled, anddiluted to 25 mL with CHO cell tissue culture medium and placed in a 125mL shake flask. The flask was placed in an incubator on a shaker at 37°C., 5% CO₂ with shaking at 120 RPM.

The CHO cells were subjected to nutrient selection and amplification to200 nM Methotrexate (MTX). Tagged protein expression was confirmed byWestern blot, and the CHO cell pool was scaled-up for harvests forprotein purification.

Example 8 Purification of Untagged FcγRIA

The following method applies to the purification of untagged FcγR1A fromCHO DXB11 cell conditioned media.

A. IgG Affinity Chromatography

Undiluted (1×) media were harvested and were loaded over a columncontaining IgG Sepharose 6 Fast Flow resin (GE Healthcare) at a flowrate of 15 cm/h. For 10 L of conditioned media, a 5 cm diameter columncontaining 150 mL of packed resin was employed. After loading the media,the column was washed at 100 cm/h with 1.6 mM citric acid, 23 mM dibasicNaPO₄, 150 mM NaCl pH 7.0 until the absorbance at 215 nm and A280 nmreturned to baseline for at least 2 column volumes (CV). Elution ofbound protein was achieved using a 10 CV descending pH gradient of 20 mMcitric acid, 5 mM dibasic NaPO₄, 0.05% Tween 20, pH 3.0 at a flow rateof 61 cm/h. Fractions containing FcγRIA were identified by SDS-PAGE andWestern blotting, were neutralized by the addition of 2 M Tris pH 7.0 toa 0.2 M final concentration and brought to 100 mM NaCl by the additionof 4 M NaCl.

B. Cation Exchange Chromatography

The Tween-20 was removed from the FcγR1A pool by HS50 chromatography.The FcγRIA elution pool was adjusted to 10 mM MES pH 6.0 using solid MESand HCl and was diluted to <5 mS/cm using 10 mM MES pH 6.0. TheFcγR1A-containing pool was loaded over an HS50 column to achievequantitative capture at a flow rate of 141 cm/h and the resin was washedat 382 cm/h with 10 mM MES pH 6.0 until A215 and A280 nm UV signalsreturned to baseline for at least 5 CV. Bound FcγR1A was eluted at 382cm/hr with a gradient of increasing NaCl concentration using 5 CV to amaximum of 60% elution buffer which consisted of 10 mM MES, 2 M NaCl pH6.0. Fractions were collected and FcγRIA was identified by SDS-PAGE andWestern blotting.

C. Size Exclusion Chromatography

The amount of protein as assessed by absorbance at 280 nm and theFcγR1A-containing fraction of the buffer-exchanged HS50 elution pool wasconcentrated using a 30 kD molecular weight cutoff (MWCO) Ultracelcentrifugal concentrator or a YM30 63.5 mm stirred cell membranedepending on the amount of FcγR1A present. The final concentrate volumewas no more than 3% of the volume of gel filtration column used. Theconcentrated FcγR1A pool was injected onto a Superdex 75 column (for <1mg FcγRIA, the column size was 10/300 mm; for 1-10 mg, the column sizewas 16/60 mm; and for >10 mg, the column size was 26/60 mm) and theprotein was eluted isocratically at a flow rate of 34-76 cm/h. Themobile phase used was 35 mM NaPO₄, 120 mM NaCl pH 7.2. Fractions werecollected and FcγRIA was identified by SDS-PAGE and Western blotting.The FcγRIA-containing fractions were concentrated to 20 mg/mL finalconcentration as described above, passed through a 0.22 μmsterile-filter, and stored at −80° C. The identity of the FcγRIA wasconfirmed by N-terminal sequencing and amino acid analyses. N-terminalsequence analysis showed that the mature protein starts with apyro-glutamic acid, which is post-translationally converted from theglutamine residue at amino acid position 16.

Example 9 Anti-Inflammatory Activities of Soluble FcγRIA

A. Immune Complex Precipitation

Chicken egg ovalbumin (OVA) was dissolved to a final concentration of15.0 g/mL in phosphate buffered saline (PBS) and combined with 300 μgrabbit polyclonal anti-OVA antibodies/mL in a final volume of 200 μL inthe presence and absence of the indicated concentration of solubleFcγRIA. Immediately thereafter, turbidity of the reaction mixture wasmonitored at 350 nm every 30 seconds for 5-10 min at 37° C. with the aidof a spectrophotometer. Linear regression was used to calculate theslope of the linear portion of the turbidity curves and theFcγR-mediated inhibition of immune complex precipitation was expressedrelative to incubations containing anti-OVA and OVA alone.

B. Cytokine Secretion from Mast Cells

Immune complexes were prepared by mixing 300 uL of rabbit polyclonalanti-OVA with 75.0 μL of 1 mg OVA/mL in PBS in a final volume of 5.0 mLof PBS. After incubation at 37° C. for 30-60′, the mixture was placed at4° C. for 18-20 h. The immune complexes were collected by centrifugationat 12,000 rpm for 5.0 min, the supernatant fraction was removed anddiscarded, and the immune complex precipitate was resuspended 1.0 mL ofice cold PBS. After another wash, the immune complexes were resuspendedin a final volume of 1.0 mL ice cold PBS. Protein concentration wasdetermined using the BCA assay.

MC/9 cells were sub-cultured in Medium A (DMEM containing 10% fetalbovine serum, 50.0 μM B-mercaptoethanol, 0.1 mM non-essential aminoacids, 1.0 mM sodium pyruvate, 36.0 μg/mL L-asparagine, 1.0 ng/mLrmIL-3, 5.0 ng/mL rmIL-4, 25.0 ng/mL rmSCF) to a density of 0.5−3×10⁶cells/mL. Cells were collected by centrifugation at 1500 rpm for 5.0 minand the cell pellet was washed in Medium A (without cytokines) andresuspended in Medium A at 2.0×10⁶ cells/mL. Aliquots of cells (2.0×10⁵cells) were incubated with 10.0 μg/well of OVA/anti-OVA immune complexes(IC's) in a final volume of 200 μL of Buffer A in a 96-well microtiterplate. After 4.0 h at 37° C., the media was removed and centrifuged at1500 rpm for 5.0 min. The cell-free supernatant fractions were collectedand aliquots were analyzed for the presence of IL-6, IL-13, TNFα, andMCP-1 cytokine release using a Luminex cytokine assay kit.

C. Complement-Mediated Lysis of SRBCs

Antibody-sensitized SRBCs (Sigma-Aldrich, St. Louis, Mo.) were preparedand were incubated with different concentrations of soluble FcγRIA.After 15 minutes at 4° C., a 25 μL sample of a 1:50 dilution of ratserum (Sigma-Aldrich, St. Louis, Mo.) was added, and hemolysis wasmeasured by monitoring the absorbance of the mixture at 540 nm asdescribed by the manufacturer.

D. Measurement of FcγRIA-CH6 Affinity for Human IgG1

The IgG1 antibody was immobilized to a single flow cell, utilizing asecond non-derivatized cell as the blank reference. Immobilization ofthe IgG1 antibody was performed using an amine coupling kit (Biacore)and the standard Wizard Template for Surface Preparation, operated bythe Biacore Control Software. Based on Wizard results for a pH scoutingstudy, the IgG1 antibody solution was diluted to 11 μg/mL in sodiumacetate, pH 5.0. The Wizard Template for amine coupling was used toimmobilize the antibody to a single flow cell. The carboxyl groups onthe sensor surfaces were then activated with an injection of a solutioncontaining 0.2 M N-ethyl-N′-(3-diethylamino-propyl) carbodiimide (EDC)and 0.05 M N-hydroxysuccinimide (NHS). The antibody solution was theninjected over the activated surface targeting a level of 150-200 RU. Theimmobilization procedure was completed by blocking remaining ester siteson the carboxymethyl dextran surface with 1 M ethanolaminehydrochloride.

The method for injection of the analyte solutions (FcγRIA-CH6) waswritten using the Biacore Wizard Template for kinetic analysis. Themethod was run at 25° C. and the samples stored in the autosampler atambient temperature. It is noted that in using the Wizard Template,certain parameters optimal for kinetics, such as injection modes, arepre-defined by the Wizard program.

The method for analysis of FcγRIA was optimized for determination ofkinetic rate constants, k_(a) and k_(d). The receptor was injected overboth flow cells (i.e., 1 and 2, blank and antibody-derivatized,respectively) in series to allow for comparative analysis of binding ofthe FcγRIA to the human IgG1 antibody vs. binding of the FcγRIA to thenon-modified control surface (binding to rabbit anti-OVA IgG nottested). The analyte was injected at a flow rate of 40 μL/min for 3minutes (association time). The dissociation time for each analyteinjection was 3 minutes. The analyte dose response curve range was0.16-10.3 nM. For each dose response curve point, N=2 replicateinjections were run. The sequence included injections of buffer forsubtraction of instrument noise and drift. Dose response curve sampleswere injected in random mode. For kinetic analysis of FcγRIA, each doseresponse curve cycle was followed by a single 30 second injection ofglycine, pH 1.75 at 50 μL/minute to regenerate the IgG antibody surface.

Data analysis was performed using Biacore Control, Evaluation andSimulation software. Baseline stability was first assessed to ensurethat the regeneration step provided a consistent binding surfacethroughout the sequence of injections. The level of non-specific bindingof the FcγRIA analyte to the control surface was checked and confirmedto be minimal. Binding curves were processed by subtraction of thecontrol surface curve (i.e., flow cell 1) from the specific bindingsurface curve (i.e., flow cell 2), as well as subtraction of instrumentnoise and drift using a buffer injection curve. The data was checked forreproducibility of analyte injections and the resulting correctedbinding curves were then globally fitted to binding models and theresulting fit and equilibrium constants evaluated.

E. Cutaneous Reverse Passive Arthus Reaction in Mice

Ten-week old female C57BL/6 mice (n=8 mice per group) were anesthetizedwith isoflurane, their dorsal skin was shaved, and the back of eachmouse was wiped with 70% alcohol. Each mouse received two intradermalinjections of 0.02 mL each, at distinct sites in the dorsal skin. Theinjection solutions contained phosphate buffered saline (PBS) and either40.0 μg of rabbit anti-ovalbumin (anti-OVA, heat-inactivated byincubation at 56° C. for 30-40 min) alone or 40.0 μg of anti-OVA and theindicated amount of FcγRIA-CH6. Mice in the control groups received twointradermal injections of 40.0 μg non-immune rabbit IgG(heat-inactivated as described above). Antibody preparations werecentrifuged at 14,000 rpm for 10 min to remove particulates prior toinjection. Immediately following the intradermal injections, each mousewas injected in the tail vein with 100.0 μL of a solution containing10.0 mg OVA/mL and 10.0 mg Evan's Blue/mL. In some instances, the tailvein injection solution also contained dexamethazone at a dose of 1.0mg/kg. Four hours after the injections, the mice were euthanized by CO₂gas. Cutaneous edema was evaluated by measuring the area of vascularleak of Evan's Blue dye (mm²) and by measuring tissue weights (mg) ofpunch biopsies taken from the lesion sites. The tissue samples were thenquickly frozen in liquid N₂ and stored at −80° C.

Neutrophil infiltration was assessed by measuring myeloperoxidaseactivity in the punch biopsy samples as described (Bradley et al., J.Invest. Dermatol. 78:206-209, 1982) using the Myeloperoxidase Assay Kitfrom Cytostore (Calgary, Alberta Canada).

Systemic administration of FcγRIA-CH6 in mice was performed byintravenous injection of either vehicle alone or vehicle containing theindicated concentrations of FcγRIA-CH6. Each mouse received theindicated dose of FcγRIA-CH6 in a 0.1 mL final volume of formulationbuffer (35 mM sodium phosphate, 120 mM NaCl, pH 7.2) 1.0-h prior toinitiating the Arthus reaction. The cutaneous Arthus reaction in micewas performed exactly as described above.

F. Results and Discussion

To evaluate whether FcγRIA-CH6 could block immune complex precipitation,an anti-OVA/OVA immune complex precipitation assay was established basedon the methods of MØller (Immunology 38:631-640, 1979) and Gavin et al.(Clin. Exp. Immunol. 102:620-625, 1995). Incubation of anti-OVA and OVAat 37° C. produced a time-dependent increase in optical density of thesolution mixture (FIG. 1, circles), an observation consistent with theformation of insoluble anti-OVA/OVA immune complexes. Addition ofFcγRIA-CH6 at the start of the assay produced a dose-dependent reductionin immune complex precipitation (FIG. 1, triangles and squares). Immunecomplex precipitation was completely abolished by 1500 nM FcγRIA-CH6.Identical data were obtained when untagged, recombinant soluble FcγRIAwas used. Since the precipitation of antigen:antibody immune complexesappears to be dependent on non-covalent interactions between theantibody Fc heavy chains (MØller, Immunology 38:631-640) and Fcγreceptors bind to the Fc portion of antibodies (Dijstelbloem H M et al.,Trends Immunol. 22:510-516, 2001), these data suggest that solubleFcγRIA disrupts immune complex precipitation by binding to the Fcportion of the anti-OVA antibodies.

To directly evaluate the interaction of FcγRA-CH6 with antibody Fc, thebinding of FcγRIA-CH6 to immobilized human IgG1 was assessed by surfaceplasmon resonance analyses. A monoclonal human IgG1 antibody wasimmobilized to the sensor surface in a single flow cell at an RU(resonance units) level of 485, a density level within optimal levelsfor kinetic analysis of FcγRIA-CH6, presuming a binding stoichiometry ofone FcγRIA molecule with one IgG1 molecule (Woof and Burton, Nature Rev.Immunol. 4:1-11, 2004). FcγRIA rapidly bound to immobilized IgG1 withrates of association and dissociation of 2.8×10⁶ M⁻¹s⁻¹ and 4.6×10⁻⁴s⁻¹, respectively, values which yield a calculated equilibriumdissociation constant of 1.7×10⁻¹⁰ M. These data are similar to thosereported previously (Paetz A et al., Biochem. Biophys. Res. Commun.338:1811-1817, 2005) and demonstrate that FcγRIA-CH6 binds with highaffinity to human IgG1.

Mast cells are thought to mediate immune complex-mediated inflammationin a variety of immune disorders such as type II hypersensitivityreactions (Ravetch, J. Clin. Invest. 110:1759-1761, 2002; Sylvestre andRavetch, Immunity 5:387-390, 1996; Jancar and Crespo, Trends Immunology26:48-55, 2005). Binding of immune complexes to mast cell Fcγ receptorsis thought to induce the secretion of pro-inflammatory cytokines, suchas IL-6 and TNFα (Ravetch, supra; Jancar and Crespo, supra), whichsubsequently leads to neutrophil infiltration and tissue damage. Toevaluate whether cytokine secretion from mast cells could be stimulatedby immune complexes, the murine mast cell line MC/9 was incubated in thepresence and absence of preformed rabbit anti-OVA/OVA immune complexes.Incubation with anti-OVA/OVA immune complexes produced a time andconcentration dependent increase in the accumulation of the inflammatorycytokines IL-6, IL-13, TNFα, and MCP-1 within the MC/9 cell conditionedmedia. Cytokine production was not altered, in contrast, when MC/9 cellswere incubated with an equivalent concentration of rabbit anti-OVA IgGalone. These data demonstrate that MC/9 cells respond to immunecomplexes by the production of inflammatory cytokines.

Incubation of MC/9 cells with anti-OVA/OVA immune complexes in thepresence of increasing amounts of FcγRIA-CH6 produced dose-dependentreductions in the accumulation of IL-6 (FIG. 2A), IL-13 (FIG. 2B), TNFα(FIG. 2C) and MCP-1 (FIG. 2D). Identical data were obtained whenuntagged, recombinant soluble FcγRIA was used. These data demonstratethat soluble FcγRIA can block the binding and signalling of immunecomplexes in mouse mast cells.

Soluble FcγRIA was also evaluated for its effect on complement-mediatedlysis of antibody-sensitized SRBCs. Incubation of antibody-sensitizedSRBCs with rat serum at 37° C. resulted in complement activation andlysis of the SRBCs. Addition of FcγRIA-CH6 to the incubation mixturesblocked SRBC lysis in a dose-dependent manner. Little or no inhibitionof hemolysis was observed, in contrast, with an unrelated controlprotein, TACI-Ig.

The findings described above demonstrate that FcγRIA-CH6 can block theformation of immune complexes in vitro, can inhibit immunecomplex-mediated signalling in mast cells, and can block IgG-mediatedcomplement activity. These data suggest that FcγRIA-CH6 may be effectiveat blocking IgG- or immune complex-mediated inflammation in an in vivosetting. To test this, the cutaneous reversed passive Arthus reactionwas established in mice and the effects of FcγRIA-CH6 on immunecomplex-mediated edema and neutrophil infiltration were assessed.

Relative to intradermal injection of an equivalent concentration ofnonimmune IgG, injection of anti-OVA antibodies produced a time andconcentration increase in edema within the skin of treated mice. Edemawas evident as both an increase in the area of extravasation of Evan'sblue dye (FIG. 3A) and in tissue weights (FIG. 3B). These effects werespecific for immune complexes as no edema was observed in the absence oftail vein injection of OVA. Accumulation of neutrophils within thelesion site, measured by extractable activity of myeloperoxidase, wasalso increased (FIG. 3C).

Intradermal delivery of anti-OVA antibodies with increasing amounts ofFcγRIA-CH6 produced a concentration-dependent reduction in edema,measured by either a decrease in Evan's blue area (FIG. 3A) or adecrease in tissue weight of the lesion site (FIG. 3B). Myeloperoxidaseactivity in the lesion biopsies was also significantly decreased byFcγRIA-CH6 (FIG. 3C). These data demonstrate that FcγRIA-CH6 was aneffective inhibitor of immune complex-induced inflammation in the Arthusreaction in mice.

These data demonstrate that local delivery of FcγRIA-CH6 can blockimmune complex-mediated dermal inflammation in the Arthus reaction inmice.

To evaluate whether systemic delivery of FcγRIA-CH6 could reducecutaneous inflammation, mice were injected with FcγRIA-CH6 via the tailvein, 1.0-h prior to initiating the Arthus reaction. Compared toinjection with vehicle alone, injection with FcγRIA-CH6 produceddose-dependent reductions in edema, measured either by the anti-OVAinduced extravasation of Evan's Blue dye (FIG. 4) or by the anti-OVAinduced increases in tissue weights of the lesion sites (FIG. 5). Withthe highest dose of FcγRIA-CH6, edema was virtually abolished (FIGS. 4and 5). Similar to the data described above, intradermal delivery of13.0 μg of FcγRIA-CH6 also reduced edema in this model (FIGS. 4 and 5).The reduction in edema seen with the highest dose of FcγRIA-CH6 given bythe intravenous route was similar to that observed with intradermaldelivery of 13.0 μg of FcγRIA-CH6 (FIGS. 4 and 5). Accumulation ofneutrophils within the lesion sites, measured by extractablemyeloperoxidase activity was also abolished in animals treated withFcγRIA-CH6.

Example 10 Comparison of the Anti-Inflammatory Activities of RecombinantHuman FcγRIA, FcγRIIA, and FcγRIIIA

In addition to the evaluation of monomeric FcγRIA-CH6 foranti-inflammatory activities (see Example 9, supra), monomericFcγRIIA-CH6 and FcγRIIIA-CH6 (prepared as described above in Example 4)were also tested using the same in vitro and in vivo assays described inExample 9. Soluble FcγRIIA-CH6 and FcγRIIIA-CH6 were tested in parallelwith FcγRIA-CH6 for their effects on immune complex precipitation,cytokine secretion from mast cells, and IgG-mediated complementactivity. Similar to FcγRIA-CH6, both FcγRIIA-CH6 and FcγRIIIA-CH6reduced immune complex precipitation, blocked complement-mediated lysisof antibody-sensitized red blood cells, and inhibited immunecomplex-mediated accumulations of IL-6, IL-13, MCP-1 and TNF-α in mastcell-conditioned media. The relative order of potency with respect tothe reduction in immune complex precipitation wasFcγRIIIA>FcγRIA>FcγRIIA, with maximal inhibition seen using 1-1.5 μM foreach soluble FcγR, a molar ratio of FcγR:anti-OVA of approximately 1:1.The relative order of potency for both the blockade ofcomplement-mediated lysis and inhibition of mast cell cytokine secretionwas FcγRIA>FcγRIIIA>FcγRIIA. With respect to inhibition of cytokinesecrection, for each soluble FcγR, the IC₅₀s were similar for eachcytokine examined.

FcγRIIA-CH6 and FcγRIIIA-CH6 were also tested in parallel withFcγRIA-CH6 for their effects in vivo on edema and neutrophilinfiltration in the cutaneous Arthus reaction in mice. In contrast tothe reduction in inflammation observed with soluble FcγRIA-CH6, neitherFcγRIIIA-CH6 nor FcγRIIA-CH6, used over a similar concentration range,reduced anti-OVA induced extravasation of Evan's blue dye, tissueweight, or tissue MPO activity (see FIG. 6, A-C).

Dimeric Fc5 fusion protein versions of FcγRIIA and FcγRIIIA, eachcontaining two molecules of the extracellular domains of FcγRIIA orFcγRIIIA fused to an effector negative version of human Fc (Fc5), werealso prepared and tested in the assays described above. The nucleotideand encoded amino acid sequences for FcγRIIA-Fc5 are shown in SEQ IDNO:35 and SEQ ID NO:36, respectively, while the nucleotide and encodedamino acid sequences for FcRIIA-Fc5 are shown in SEQ ID NO:37 and SEQ IDNO:38, respectively. N-terminal sequence analysis showed Gln-34 as thestart site for mature FcγRIIA-Fc5 and Met-18 and Glu-21 as the startsite for mature FcγRIA-Fc5. Each of the dimeric Fc5 fusion proteins hadactivities similar to the monomeric versions of each protein in all ofthe in vitro assays described above. Similar to their monomericcounterparts, and again in contrast to FcγRIA-CH6, neither FcγRIIA-Fc5nor FcγRIIIA-Fc5 reduced inflammation or neutrophil infiltration in thereverse passive Arthus reaction in mice.

Example 11 Collagen Antibody-Induced Model of Arthritis

Male DBA/1 J mice (8 weeks old, n=8 mice per group) were administered 2mg (in 200 uL) of the anti-Type II collagen antibody cocktail (ChemiconIntl. Arthrogen-CIA®) via intravenous tail injection on Day 0. Theamount of mAb cocktail injected was based on literature values and ondata from preliminary studies where 2.0 mg doses of Arthrogen-CIA® gaveclear and consistent symptoms of arthritis in male DBA/1 mice. Threedays later, mice received sub-cutaneous injections of either vehiclealone (PBS) or vehicle containing the indicated concentration (0, 0.67,or 2.0 mg) of FcγRIA-CH6. Three and one-half hours later, all micereceived an intraperitoneal injection of 50 ug of LPS dissolved in afinal volume of 50 uL of PBS, as provided in the Arthrogen kit. Micewere treated with vehicle or the indicated concentration of FcγRIA-CH6every other day for a total of five doses.

Mice were scored (visual scores and caliper paw measurements) forarthritis on a daily basis starting on day 0, prior to injection of theArthrogen-CIA® antibody cocktail. Mice were be sacrificed on day 11.Serum was collected and frozen at −80 C. Paws were collected into 10%NBF, and processed for histology.

Treatment of mice with the Arthrogen-CIA® antibody cocktail, produced atime-dependent increase in paw inflammation, measured by either thevisual paw score (FIG. 7, PBS treated) or by paw thickness (FIG. 8, PBStreated). The increase in arthritis score is easily observed in animalstreated with vehicle alone (PBS). Treatment of animals with FcγRIA-CH6produced a concentration-dependent reduction in paw inflammation.Antibody-induced inflammation, evident as the visual paw score (FIG. 7)or paw thickness (FIG. 8), was completely abolished by the highest doseof FcγRIA-CH6 administered. A less robust reduction in these parameterswas seen with the 0.67 mg dose of FcγRIA-CH6 administered. These datademonstrate that FcγRIA-CH6 has potent anti-inflammatory properties in asetting of arthritis.

Example 12 Treatment of Cryoglobulinemia with Soluble Hybrid FcγR inTSLP Transgenic Mice

Mice over-expressing thymic stromal lymphopoietin (TSLP), aninterleukin-7 (IL-7)-like cytokine with B-cell promoting properties,produce large amounts of circulating cryoglobulins of mixed IgG-IgMcomposition. (See Taneda et al., Am J. Pathol. 159:2355-2369, 2001.)Development of mixed cryoglobulinemia in these animals is associatedwith systemic inflammatory disease involving kidneys, liver, lungs,spleen, and skin (see id.) due to immune complex deposition in thesetissues. Kidney disease in these animals closely resembles humancryoglobulinemia glomerulonephritis as seen in patients with HCVinfection. A role for Fcγ receptors in the disease process was shown bythe exacerbation of renal injury with accelerated morbidity andmortality after deletion of the inhibitory receptor Fcγ receptor IIb(see Muhlfeld et al., Am. J. Pathol. 163:1127-1136, 2003). In view ofthese data, the studies described herein, demonstrating efficacy ofsoluble FcγRIA against immune-complex-mediated inflammation, suggestthat TSLP-transgenic mice are a suitable model for evaluating efficacyof soluble FcγRIA or soluble hybrid FcγR as described herein fortreating cryoglobulinemia.

Groups of ten TSLP-transgenic mice (three to six weeks of age) aretreated with either vehicle alone, or vehicle containing 0.1, 0.3, 0.9,or 2.0 mg of soluble hybrid Fcγ receptor by subcutaneous injections.Animals are dosed with either vehicle or vehicle with soluble hybridFcγR by a variety of dosing schedules (e.g., every other day over 21days or every fourth day over 21 days).

At 21 days following dosing, a urine sample is collected for measurementof albuminuria, the animals are anesthesized with halothane, and bloodis drawn by cardiac puncture. Spleen, kidneys, liver, ears, and lungsare removed and routinely processed for histology. For all organs, 4 μmsections from formalin-fixed and paraffin-embedded tissue are stainedwith hematoxylin and eosin (H&E) following routine protocols. From thekidney, 2 μm sections are stained with H&E, periodic acid Schiff reagent(PAS), and periodic acid methenamine silver stain.

Blood urea nitrogen is measured using a standard clinical chemistryanalyzer and serum stored at 4° C. is assessed for the presence ofcryoglobulins by visual inspection. Urine albumin to creatinine ratio iscalculated to evaluate albuminuria by standard procedures.

Morphometry is performed on H&E-stained and silver-stained slides andkidney damage is assessed by measuring the number of glomerular nucleiand the glomerular tuft area on H&E stained slides, the area ofglomerular matrix and glomerular tuft area on silver-stained slides, andthe area of glomerular MAC-2 positive staining for macrophages and theglomerular tuft area. Results are expressed as the cell number perglomerulus, the cell number per glomerular tuft area, the matrix area ofeach glomerulus, the percentage of matrix, the area of macrophages perglomerulus, and the area of macrophages per glomerular area.

Efficacy of soluble hybrid FcγR are measured as decreases in theglomerular tuft area, mean glomerular areas occupied by macrophages, andmean cell numbers per glomerulus, and by decreases in matrix area,compared to wild-type controls.

Example 13 FcγRIA Decreases Disease Incidence and Progression in MouseCollagen Induced Arthritis (CIA) Model

A. Mouse Collagen Induced Arthritis (CIA) Model

The CIA model of arthritis is an appropriate and well-regarded model toevaluate therapeutic potential of drugs to treat human arthritis.Arthritis is a disease that is characterized by inflammation and/orinappropriate immune complex formation with the joints. The immunecomplexes are often composed of antibodies directed against type IIcollagen, an important hyaline cartilage matrix protein. Formation ofimmune complexes within the joint leads to the recruitment of immunecells to the joint space and the generation of inflammatory cytokinesthat lead to cartilage and bone destruction within the affected joint.Collagen induced arthritis in mice thus shares many biochemical,cellular, and structural similarities with rheumatoid arthritis inhumans.

Eight to ten-week old male DBA/1 J mice (25-30 g) were used for thesestudies. On day −21, animals were given an intra-dermal tail injectionof 0.1 mL of 1 mg/ml chick Type II collagen formulated in CompleteFreund's Adjuvant (prepared by Chondrex Inc., Redmond, Wash.). Threeweeks later, on Day 0, mice were given the same injection exceptprepared in Incomplete Freund's Adjuvant. Animals began to show symptomsof arthritis following the second collagen injection, with most animalsdeveloping inflammation within 1 to 2 weeks. The extent of disease wasevaluated in each paw by using a caliper to measure paw thickness, andby assigning a clinical score (0-3) to each paw (see description belowfor disease scoring).

B. Monitoring Disease

Incidence of disease in this model was 95-100% with only a few (0-2)non-responders (determined after 6 weeks of observation). Animals areconsidered to have established disease only after marked, persistent pawswelling has developed. All animals were observed daily to assess thestatus of the disease in their paws, which was done by assigning aqualitative clinical score to each of the paws. Every day, each animalhad its 4 paws scored according to its state of clinical disease. Todetermine the clinical score, the paw is thought of as having 3 zones,the toes, the paw itself (manus or pes), and the wrist or ankle joint.The extent and severity of the inflammation relative to these zones wasnoted including: observation of each toe for swelling, torn nails orredness of toes; notation of any evidence of edema or redness in any ofthe paws; notation of any loss of fine anatomic demarcation of tendonsor bones; evaluation of the wrist or ankle for any edema or redness; andnotation if the inflammation extends proximally up the leg. A paw scoreof 1, 2, or 3 was based first on the overall impression of severity, andsecond on how many zones are involved. The scale used for clinicalscoring is shown below:

Clinical Score

-   -   0=Normal    -   0.5=One or more toes involved, but only the toes are inflamed    -   1=mild inflammation involving the paw (1 zone), and may include        a toe or toes    -   2=moderate inflammation in the paw and may include some of the        toes and/or the wrist/ankle (2 zones)    -   3=severe inflammation in the paw, wrist/ankle, and some or all        of the toes (3 zones)        C. Treatments

Established disease was defined as a qualitative score of pawinflammation ranking 1 or more. Once established disease was present,the date was recorded, designated as that animal's first day with“established disease,” and treatment started. Mice were treated withPBS, or one of the following doses of human FcγRIA (hFcγRIA; diluted inPBS to desired concentration) subcutaneously every other day for a totalof 6 doses: 2 mg; 0.667 mg; 0.22 mg, or one of the following doses ofhFcγRIA (diluted in PBS to desired concentration) subcutaneously every4th day for a total of 3 doses: 2 mg; 0.667 mg.

Blood was collected at the end of the experimental period to monitorserum levels of anti-collagen antibodies, as well as serumimmunoglobulin and cytokine levels. Animals were euthanized 48 hoursfollowing their last treatment. Blood was collected for serum, and allpaws and selected tissues were collected into 10% NBF for histology.Serum was collected and frozen at −800 C for immunoglobulin and cytokineassays.

Mice injected with type II collagen and treated with vehicle developedpaw swelling that was evident as higher disease scores (paw scores) withdays after randomization (see FIG. 10, open circles). Treatment withFcγRIA every other day for 12 days produced a statistically significant,dose-dependent reduction in clinical scores (see FIG. 10, solidsymbols). Treatment with the 0.22 mg dose produced a 50% reduction indisease progression, while the 2.0 mg dose reduced disease severity by90%. Reduction in paw scores was also seen when FcγRIA was administeredwith an extended dose interval (see FIG. 11). Compared to treatment withvehicle alone (PBS), treatment with 2.0 mg of FcγRIA every fourth dayfor 9 days produced a 50% reduction in clinical scores, compared withthe 90% reduction seen when FcγRIA was administered every other day (seeFIG. 11). Mice treated with hFcγRIA also had a dose-dependent reductionin the number of affected paws (see FIG. 12).

In summary, these results indicate that in murine collagen-inducedarthritis, administration of recombinant human FcγRIA can reduce diseaseincidence and progression. These data support the use of FcγRIA as anovel effective therapy for treatment of arthritis and other IgG- andimmune complex-mediated diseases in humans.

Example 14 FcγRIA Decreases Levels of IL-6 and Anti-type II CollagenAntibodies in Mouse Collagen Induced Arthritis (CIA) Model

In addition to monitoring disease development in the mouse CIA model byassessing the extent and severity of paw inflammation, mice used in theCIA study described above (see Example 13) were also assessed for levelsof IL-6 and anti-type II collage antibodies, as summarized below.

A. Methods

Quantitation of Serum Cytokines by Luminex Assay

The level of cytokines in mouse sera were quantitated using a Luminexcytokine assay kit from Upstate Biotechnology. Each plate was blockedwith 0.2 mL of Assay Buffer for 10 min, the buffer was removed and theplate blotted. A 0.025 mL of each standard, control, blank, and testsample was added to the appropriate wells followed by a 0.025 mL sampleof Serum Matrix. A 0.025 mL volume of Assay Buffer was added to eachsample well followed by 0.025 mL of capture beads that were suspended bysonication. Each plate was sealed, covered in foil, and incubated on ashaker at 4° C. After 18-24 h, the well contents were removed byaspiration and the plate was blotted. Each plate was then washed 2-3times with 0.2 mL of wash buffer, 0.025 mL of Detection AntibodyCocktail was added to each well and the plate was sealed, covered infoil, and incubated on a shaker at room temperature for 60 min. A 0.025mL sample of Streptavidin-Phycoerythrin was added to each well, eachplate was sealed, covered in foil, and incubated on a shaker at roomtemperature for 30 min. The contents of each well were removed byaspiration, each plate was blotted, and washed 2-3 times with 0.2ml/well of wash buffer. A 0.1 ml sample of Sheath Buffer was added toeach well and the absorbance of each sample was read on a Luminexinstrument.

Quantitation of Anti-Type II Collagen Antibodies

The level of anti-type II collagen antibodies in mouse sera werequantified using a Mouse IgG Anti-Type II Collagen Antibody Kit fromChondrex. Each plate was blocked with 0.1 mL of Blocking Buffer for 60min at room temperature. The plates were washed three times with WashBuffer and standards, samples, or blanks were added to the appropriatewells in a final volume of 0.1 mL. The plates were covered and incubatedovernight at 4° C. The next day, each plate was washed six times withWash Buffer and a 0.1 mL volume of secondary antibody was added to eachwell. The plates were then incubated at room temperature. After 2.0 h,each plate was washed and 0.1 mL of OPD solution was added to each welland incubated for 30 min at room temperature. The reactions wereterminated by adding 0.05 mL of 2N sulfuric acid to each well and theabsorbance of each well at 490 nm was determined.

B. Result

Compared to non-arthritic mice that did not receive injections oftype-II collagen, mice injected with type-II collagen had elevated serumlevels of IL-6 at the time of sacrifice on day 15. Levels of IL-6 werebelow the level of detection in normal mice and increased to 320 pg/mLin mice that developed collagen-induced arthritis and were treated withvehicle alone. Treatment with soluble human FcγRIA (2.0 mg given everyother day for two weeks) reduced the serum levels of IL-6 by 70% to 95pg/mL on day 15.

In addition to reducing the levels of IL-6, treatment with soluble humanFcγRIA also reduced the levels of anti-type II collagen antibodies inthe sera of arthritic mice. Administration of 2.0 mg of FcγRIA everyother day produced a 40-50% reduction in the amount of anti-type IIcollagen antibodies, relative to the levels observed in arthritic micetreated with vehicle alone, on day 15 at the time of sacrifice.

Example 15 Construction of Hybrid Soluble C-term Six His FcγRIAExpression Plasmids to Express the First Ig Domain of FcγRIIA, FcγRIIB,FcγRIIIA, or FcγRIIIB Followed by the 2nd and 3rd Ig Domains of FcγR1A

Expression constructs containing the first extracellular Ig domain ofFcγRIIA, FcγRIIB, FcγRIIIA, or FcγRIIIB followed by the second and thirdextracellular Ig domains of human FcγRIA with a C-terminal tag, six His(c6×H) were generated. These hybrid FcγR constructs are also referred toas FcγRIIA/RIA-CH6, FcγRIIB/RIA-CH6, FcγRIIIA/RIA-CH6, andFcγRIIIB/RIA-CH6, respectively. These constructs were generated via PCRand homologous recombination using DNA fragments encoding the first Igdomain of FcγRIIA, FcγRIIB, FcγRIIIA, or FcγRIIIB, a DNA fragmentencoding the second and third Ig domain of FcγRIA and the expressionvector pZMP31.

Four PCR fragments were generated which encoded a 5′ overlap with thepZMP31 vector sequence in the 5′ non-translated region, the first Igdomain of FcγRIIA, FcγRIIB, FcγRIIIA, or FcγRIIIB and a 3′ overlap withthe second Ig domain of FcγRIA. The PCR amplification reactions used the5′ oligonucleotides: TCCACAGGTGTCCAGGGAATTCATATAGGCCGGCCATGGCTATGGAGACCCAAATGTCT (SEQ ID NO:47; forward primer specific for FcγRIIAleader sequence),TCCACAGGTGTCCAGGGAATTCATATAGGCCGGCCATGGGAATCCTGTCATTCTTACC (SEQ IDNO:48; forward primer specific for FcγRIIB leader sequence) orTCCACAGGTGTCCAGG GAATTCATATAGGCCGGCCATGTGGCAGCTGCTCCCCCAACT (SEQ IDNO:49; forward primer specific for FcγRIIIA and FcγRIIIB leadersequence). The four PCR reactions were run with the 3′ oligonucleotidesCGTGAAGACTCTGCTGGAGACCTGCAGTAGTAGCCATTCGGAAAG CACAGTCAGATGCAC (SEQ IDNO:50; reverse primer specific for domain 1 (first Ig domain) of FcγRIIAand FcγRIIB and which includes sequence overlap with domain 2 (second Igdomain) of FcγRIA),CGTGAAGACTCTGCTGGAGACCTGCAGTAGTAGCCAGCCGATATGGACTTCTAG CTGCAC (SEQ IDNO:51; reverse primer specific for domain 1 (first Ig domain) of FcγRIAand which includes sequence overlap with domain 2 (second Ig domain) ofFcγRIA), or CGTGAAGACTCTGCTGGAGACCTGCAGTAGTAGCCAGCCGACATGGACTTCTAGCTGCAC (SEQ ID NO:52;reverse primer specific for domain 1 (first Ig domain) of FcγRIIIB andwhich includes sequence overlap with domain 2 (second Ig domain) ofFcγRIA), utilizing previously generated DNA clones for soluble FcγRIIA(MPET construct #1202), FcγRIIB (MPET construct #1204), FcγRIIIA (MPETconstruct #1205), or FcγRIIIB (MPET construct #1207) as templates.

Three additional PCR fragments were generated that encode the second andthird Ig domains of FcγRIA with a CH6 (C-terminal six-His) tag; thesefragments contained (i) a 5′ overlap with a PCR fragment encoding thefirst Ig domain of FcγRIIA, FcγRIIB, FcγRIIIA, or FcγRIIIB; (ii) anFcγRIA extracellular domain coding region (Ig domains 2 and 3); (iii)the-six His tag coding sequence; and (iv) a 3′ overlap with the pZMP31vector downstream of the MCS. The PCR amplification reactions used thefollowing 5′ oligonucleotides: CTCAGCGACCCTGTGCATCTGACTGTGCrTTCCGAATGGCTACTACTGCAGGTCTCCAGC (SEQ ID NO:53; forward primerspecific for domain 2 (second Ig domain) of FcγRIA and which includessequence overlap with the first Ig domain of FcγRIIA and FcγRIIB),CTCAGTGACCCGGTGCAGCTAGAAGTCCATATCGG CTGGCTACTACTGCAGGTCTCCAGC (SEQ IDNO:54; forward primer specific for domain 2 (the second Ig domain) ofFcγRIA and which includes sequence overlap with the first Ig domain ofFcγRIIIA), or CTCAGTGACCCGGTGCAGCTAGAAGTCCATGTCGGCTGGCTACTACTGCAGGTCTCCAGC (SEQ ID NO:55; forward primer specific for domain 2 (second Igdomain) of FcγRIA and which includes sequence overlap with the first Igdomain of FcγRIIIB). Each of the three PCR reactions were run with the3′ oligonucleotide TACAACCCCAGAGCTGTTTTAAGGCGCGCCTCTAGATTAGTGATGGTGATGGTGATGTCC (SEQ ID NO:56; reverse primer specific forthe C-terminus of the FcγRIA extracellular domain and which includes asix His tag and stop codon sequence) and a previously generated DNAclone of FcγRIA as the template (MPET construct #1198).

The PCR amplification reaction conditions were as follows: 1 cycle, 95°C., 5 minutes; 25 cycles, 95° C., 30 seconds, followed by 55° C., 30seconds, followed by 68° C., 1 minute; 1 cycle, 72° C., 7 minutes. ThePCR reaction mixtures were run on a 1% agarose gel and the DNA fragmentscorresponding to the expected size is were extracted from the gel usinga QIAquick™ Gel Extraction Kit (Qiagen, Cat. No. 28704).

The plasmid pZMP31 is a mammalian expression vector containing anexpression cassette having the chimeric CMV enhancer/MPSV promoter,FseI, NarI, and BglII sites for linearization prior to yeastrecombination, an E. coli origin of replication; a mammalian selectablemarker expression unit comprising an SV40 promoter, enhancer and originof replication, a DHFR gene, and the SV40 terminator, and URA3 andCEN-ARS sequences required for selection and replication in S.cerevisiae.

The plasmid pZMP31 was digested with FseI, NarI, and BglII prior torecombination in yeast with the following corresponding combinations ofgel extracted PCR fragments mentioned above: FcγRIIA and FcγRIA, FcγRIIBand FcγRIA, FcγRIIIA and FcγRIA, or FcγRIIB and FcγRIA. 50 μl ofcompetent yeast (S. cerevisiae) cells were combined with 3 μl of eachPCR fragment insert DNA and 30 ng of FseI, NarI and BglII digestedpZMP31 vector. The mix was transferred to a 0.2 cm electroporationcuvette. The yeast/DNA mixture was electropulsed using power supply(BioRad Laboratories, Hercules, Calif.) settings of 0.75 kV (5 kV/cm), ∞ohms, and 25 μF. Three hundred μl of 1.2 M sorbitol was added to thecuvette, and the yeast was plated in 75 μl and 200 id aliquots onto twoURA-DS plates and incubated at 30° C. After about 72 hours, the Ura+yeast transformants from a single plate were resuspended in 100 ul ofyeast lysis buffer (0.1M NaCl, 0.0062M Tris HCl, 0.0038M Tris Base,0.001M EDTA, 2% (v/v) polysorbate 20, 1% (w/v) SDS) and 100 μl of QiagenMiniPrep kit buffer P1 containing 10 U Zymolyasel/100 ul. This mixturewas then incubated at 37° C. for approximately 15 min. and the rest ofthe Qiagen miniprep kit protocol was followed according to manufacture'sinstructions.

Transformation of electrocompetent E. coli host cells (DH12S) wasperformed using 4 μl of the yeast DNA preparation and 50 μl of E. colicells. The cells were electropulsed at 1.75 kV, 25 μF, and 400 ohms.Following electroporation, 0.5 ml LB was added and then the cells wereplated in 10 μl and 30 μl aliquots on two LB AMP plates (LB broth(Lennox), 1.8% Bacto™ Agar (Difco), 100 mg/L Ampicillin).

The inserts of five DNA clones per construct were subjected to sequenceanalysis. One clone containing the correct sequence is selected.Large-scale plasmid DNA was isolated using a commercially available kit(QIAGEN Plasmid Mega Kit, Qiagen, Valencia, Calif.) according tomanufacturer's instructions. The nucleotide sequences for theFcγRIIA/RIA-CH6, FcγRIIB/RIA-CH6, FcγRIIIA/RIA-CH6, and FcγRIIIB/RIA-CH6hybrid constructs are shown, respectively, in SEQ ID NOs 39, 41, 43, and45. The corresponding encoded amino acid sequences for FcγRIIA/RIA-CH6,FcγRIIB/RIA-CH6, FcγRIIIA/RIA-CH6, and FcγRIIIB/RIA-CH6 are shown,respectively, in SEQ ID NOs 40, 42, 44, and 46.

The same process was used to prepare native soluble sequence FcγRIA(which includes the native sequence Ig domains 1, 2 and 3) with aC-terminal his tag, composed of Gly Ser Gly Gly His His His His His His(FcγRIA-CHIS). To prepare this construct, a PCR fragment encoding nativesoluble sequence FcγRIA (which includes the native sequence Ig domains1, 2 and 3) with a C-terminal his tag was generated usingoligonucleotide primer TCCACAGGTGTCCAGGGAATTCATATAGGCCGGCCATGTGGTTCTTGACAACTCTGCTC (SEQ ID NO:57; forward primerspecific for FcγRIA leader sequence), oligonucleotide primerTACAACCCCAGAGCTGTTTTA AGGCGCGCCTCTAGATTAGTGATGGTGATGGTGATGTCC (SEQ IDNO:58; reverse primer specific for C-terminus of the FcγRIAextracellular domain and which includes a 6 His tag and stop codonsequence) and a previously generated DNA clone of FcγRIA as the template(MPET construct #1198).

The Mega Prep Plasmid DNA was utilized in transient transfections of293F cells for downstream analysis of expression and aggregate levels.For each construct, 25 g of plasmid DNA was diluted into 300 μl of prewarmed 37° C. Optimem media (Invitrogen) and allowed to incubate at roomtemperature for 5 min. In a separate tube 32 ul of Lipofectamine 2000(Invitrogen) was diluted into 300 μl pre warmed Optimem media andallowed to incubate at room temperature for 5 min. The contents of thetwo tubes were added together and mixed and allowed to incubate at roomtemperature for 30 min. with occasional, gentle mixing. After theDNA/lipofectamine complexes were formed, they were added to 25 ml of293F cells at 1×10⁶ cells/ml cultured in Invitrogen Freestyle media. Theculture was allowed to proceed for 96 hrs and the media was harvested bypelleting the cells via centrifugation for 5 min. at low speed. Themedia was saved and passed on for expression and aggregation levelanalysis (see Example 16, infra).

Example 16 Analysis of Soluble Hybrid FcγR Constructs from Transient293F Conditioned Media

Soluble FcγRIA protein has a tendency to form self-associated complexesand aggregates under normal cell culture temperatures. Soluble forms ofother Fcγ receptor family members (FcγRIIA, FcγRIIB, FcγRIIA, FcγRIIIB)do not appear to show the level of self-association that FcγRIA does.

Soluble hybrid FcγR constructs were generated where the first Ig domainof FcγRIA was replaced with the first Ig domain of one of the otherfamily members (FcγRIIA, FcγRIIB, FcγRIIIA, FcγRIIIB), as describedabove (see Example 15). These hybrid constructs (FcγRIIA/RIA-CH6,FcγRIIB/RIA-CH6, FcγRIIIA/RIA-CH6, and FcγRIIIB/RIA-CH6) weretransiently transfected into 293F cell lines, and the conditioned mediafrom those cells were assessed for expression and capture onIg-Sepharose Resin (GE Healthcare, Uppsala, Sweden). Soluble, nativeversions of other family members were also expressed and analyzed insimilar fashion.

IgG Sepharose has been shown experimentally to only bind monomeric,non-aggregated FcγRIA. Accordingly, the ability of various FcγRconstructs to bind IgG Sepharose was used as a measure of eachconstruct's tendency to self-aggregate (where increased binding to IgGSepharose indicates decreased tendency to self-aggregate).

Conditioned media expressing the native and hybrid constructs wassubjected to binding to IgG Sepharose in batch mode. 300 uL of packedresin was pre-eluted using 19.9 mM Citric Acid (EMD, Darnstadt,Germany), 5.1 mM Dibasic NaPO₄, 150 mM NaCl, 0.05% Tween 20 (EM Science,Darnstadt, Germany) pH 3.0, and then equilibrated in 1.61 mM CitricAcid, 23.4 mM Dibasic NaPO₄, 150 mM NaCl pH 7.0.

The equilibrated resin was combined with 10-25 mL of conditioned mediaand incubated for 1 hour at 4° C. while slowly turning. After 1 hour,the mixture was transferred to a BioRAD Econo-column (Hercules, Calif.)and the flow-through collected in a separate vessel via gravity flow.The resin was then washed with 80 column volumes using equilibrationbuffer. Bound protein was eluted using 4 mL of elution buffer,incubating the resin for roughly 5 minutes before collecting the elutionfraction. The resin was chased with another 1 mL of elution buffer, andthat chase volume was collected in the same vessel as the elutionfraction. The elution fraction was neutralized using 0.5 mL 2M Tris pH8.0.

Load, flow-through, and elution fractions were further analyzed viawestern blot under non-reducing conditions, where the prepped sampleswere also not heated in any way. Samples were loaded onto 4-12% Bis-Trisgel using MES running buffer (Invitrogen, Carlsbad, Calif.), normalizingall for volume, and the gel was run at constant 150V. SDS-PAGE gel wasthen transferred to 0.2 μm nitrocellulose using the I-Blot system(Invitrogen). Non-specific sites on the blot were then blocked using2.5% non-fat dry milk (NFDM) in Western A buffer (0.097% (w/w) TRISbase, 0.661% (w/w) Tris HCl, 0.18612% (w/w) EDTA, 0.05% (v/w) Igepal,0.877% (w/w) NaCl, 0.25% Gelatin). The blot was probed with anti-FcγR1/CD64 monoclonal antibody (R&D, Minneapolis, Minn.) diluted 1:1000 in2.5% NFDM in Western A buffer and then anti-Murine JgG-HRP (Santa CruzBiotech, Santa Cruz, Calif.), incubating each for 1 hour at roomtemperature with washes of Western A buffer between incubations. Asprepped, the samples were analyzed for percent of target in the flowthrough (aggregate amount) and percent in the elution pool (monomeramount) as compared to the total expressed in the load (aggregate andmonomer). This analysis was performed on the ImageQuant RT ECL imagerrunning the ImageQuant TL v2005 software (GE Healthcare, Uppsala,Sweden).

Two FcγR hybrid constructs showed improvement in the amount of aggregateand monomer expressed (i.e., decreased amount of aggregate and increasedamount of monomer) when compared to native soluble FcγRIA. Native,soluble FcγRIA showed an average aggregate amount of 66% of the totalexpressed, with 21% of the total expressed being recovered from the IgGresin (13% of the total expressed was not accounted for). TheFcγRIIA/RIA hybrid showed an average aggregate amount of 14.2% and anIgG recovered amount of 40% (48% was unaccounted for). The FcγRIIIA/RIAhybrid showed an average aggregate amount of 36% with 82% beingrecovered from the IgG resin. These results are represent an n=2.

Example 17 Expression of Soluble Hybrid FcγR Constructs in CHO Cells

For the hybrid constructs with sequence for soluble C-terminal six-hisFcγRIA to express the first Ig domain of FcRIIA or FcγRIIA, followed bythe second and third Ig domains of FcγRIA (see Example 15), 600 g ofeach of the expression constructs (mega prep plasmid) were digested with720 units of BstB1 restriction enzyme at 37° C. for 2.5 hours, washedwith phenol/chloroform/isoamyl alcohol, followed by a wash withchloroform/isoamyl, then precipitated overnight with ethanol, andcentrifuged in a 1.5 mL microfuge tube. The supernatants were decantedand the pellets were washed with 1 mL of 70% ethanol and allowed toincubate for 5 minutes at room temperature. The tubes were spun in amicrofuge for 10 minutes at 14,000 RPM and the supernatants weredecanted off the pellets. In the sterile environment on the tissueculture hood, the pellets were allowed to dry in the open air for apx. 5min, then resuspended in 1.2 mls of 37° C., pre-warmed CHO cell tissueculture medium and allowed to incubate at 37° C. for 10 minutes. Whilethe DNA pellets were being solublized, approximately 5.6×10⁷ CHO cellswere pelleted and resuspended in 2.4 mls of CHO cell tissue culturemedium. Each solublized plasmid preparation was divided into three 400μl volumes and then 400 μl of the CHO cell suspension was added for afinal volume of 8001. The DNA/cell mixtures were placed in a 0.4 cm gapcuvette and electroporated using the following parameters; 950 μF, highcapacitance, at 300 V. For each plasmid electroporation set, thecontents of the cuvettes were then removed, pooled, and diluted to 25mLs with CHO cell tissue culture medium and placed in a 125 mL shakeflask. The flask was placed in an incubator on a shaker at 37° C., 5%CO₂ with shaking at 120 RPM.

The CHO cells were subjected to nutrient selection and amplification to500 nM Methotrexate (MTX). The selected CHO lines were designated MECL1308 (FcγRIIA/IA hybrid) and 1309 (FcγRIA/IA hybrid).

To test for expression, cultures were set up using passage 7post-electroporation pools. Cells were centrifuged and resuspended infresh media in a 50 ml volume at 0.6×10⁶ cells/ml and allowed to proceedas previously described for 96 hrs. Tagged protein expression wasconfirmed by Western blot.

Example 18 Expression of FcγRIIA/IA-CH6 Protein in CHO DXB11 Cells in aWave Reactor

FcγRIIA/IA-CH6 protein was expressed in a 10 L Wavebag Reactor (WaveBiotech) in CHO DXB11 cells transfected with the ZG construct 1892. Thecells were scaled up in shake flasks using ZM2 medium (SAFC BiosciencesEx-CELL catalog #68041) with the addition of 5 mM L-glutamine (from 200mM L-glutamine, Gibco catalog #25030-081), 1 mM sodium pyruvate (from100 mM Sodium Pyruvate, Gibco catalog #11360-070) and 500 nMmethotrexate. The reactor run was initiated by seeding 500 mL of shakeflask culture in log phase into 4.5 L ZM2 medium containing L-glutamineand sodium pyruvate but no methotrexate. This resulted in a 5 L finalworking volume with a density of 3.5×10⁵ cells/mL.

The CO₂ level was maintained at 3%-6% and was pumped continually intothe headspace of the reactor at 0.2 LPM. Dissolved oxygen requirementsof the cells were met by rocking the culture on a platform at a rate of25 rocks per minute at an angle setting of 9.5. pH was not controlledbut stayed between 6.6 and 7.0. Temperature was maintained at 37° C.until density reached 2.0×10⁶ cells/mL, then temperature was dropped to34° C. for the remainder of the run. Glucose levels were maintainedabove 2 g/L and L-glutamine above 2 mM.

The culture was harvested 11 days after seeding with a density of7.5×10⁶ cells/mL and 96% viability. The supernatant was centrifuged at3500×g for 15 minutes and the clarified conditioned medium was passedthrough a 0.22 μm filter (Millipore Opticap catalog #KWSSL4HB3) andsubmitted for protein purification.

Example 19 Expression of FcγRIIIA/IA-CH6 Protein in CHO DXB11 Cells in aWave Reactor

FcγRIIIA/IA-CH6 protein was expressed in a 10 L Wavebag Reactor (WaveBiotech) in CHO DXB11 cells transfected with the ZG construct 1894. Thecells were scaled up in shake flasks using ZM2 medium (SAFC BiosciencesEx-CELL catalog #68041) with the addition of 5 mM L-glutamine (from 200mM L-glutamine, Gibco catalog #25030-081), 1 mM sodium pyruvate (from100 mM Sodium Pyruvate, Gibco catalog #11360-070) and 500 nMmethotrexate. The reactor run was initiated by seeding 500 mL of shakeflask culture in log phase into 4.5 L ZM2 medium containing L-glutamineand sodium pyruvate but no methotrexate. This resulted in a 5 L finalworking volume with a density of 3.1×10⁵ cells/mL.

The CO₂ level was maintained at 3%-6% and was pumped continually intothe headspace of the reactor at 0.2 LPM. Dissolved oxygen requirementsof the cells were met by rocking the culture on a platform at a rate of25 rocks per minute at an angle setting of 9.5. pH was not controlledbut stayed between 6.6 and 7.0. Temperature was maintained at 37° C.until density reached 1.4×10⁶ cells/mL, then temperature was dropped to34° C. for the remainder of the run. Glucose levels were maintainedabove 2 g/L and L-glutamine above 2 mM.

The culture was harvested 11 days after seeding with a density of6.3×10⁶ cells/mL and 97% viability. The supernatant was centrifuged at3500×g for 15 minutes and the clarified conditioned medium was passedthrough a 0.22 μm filter (Millipore Opticap catalog #KWSSL4HB3) andsubmitted for protein purification.

Example 20 Purification of Soluble FcγRIA and FcγRIIIA/IA-CH6

Large scale production of rh-FcγRIA and FcγRIIIA/IA-CH6 was performed in10 L Wavebag Reactor (Wave Biotech). Cells were scaled up in shakeflasks using ZM2 medium (SAFC Biosciences Ex-CELL) with the addition of5 mM L-glutamine, 1 mM sodium pyruvate, and 500 nM methotrexate. Thereactor run was initiated by seeding 500 mL of shake flask culture inlog phase into 4.5 L ZM2 medium containing L-glutamine and sodiumpyruvate but no methotrexate. This resulted in a 5 L final workingvolume with a density of 3.1×10³ cells/mL. The CO₂ level was maintainedat 3%-6% and was pumped continually into the headspace of the reactor at0.2 LPM. Dissolved oxygen requirements of the cells were met by rockingthe culture on a platform at a rate of 25 rocks per minute at an anglesetting of 9.5. pH was not controlled but stayed between 6.6 and 7.0.Temperature was maintained at 37° C. until density reached 1.4×10⁶cells/mL, then temperature was dropped to 34° C. for the remainder ofthe run. Glucose levels were maintained above 2 g/L and L-glutamineabove 2 mM. The culture was harvested 11 days after seeding with adensity of 6.3×10⁶ cells/mL and 97% viability. The supernatant wascentrifuged at 3500×g for 15 minutes and the clarified conditionedmedium was passed through a 0.22 μm filter (Millipore Opticap) prior toprotein purification.

Untagged rh-FcγRIA was purified by sequential chromatography onIgG-Sepharose, Poros HS-50, and Superdex 75 as described in Example 8,supra.

His-tagged FcγRIIIA/IA was purified by sequential chromatography onNi-NTA Superflow resin, Q-Sepharose, and Superdex 200. Briefly,CHO-conditioned media were sterile filtered, concentrated, and bufferexchanged into 50 mM NaPO₄, 500 mM NaCl, 25 mM imidazole, pH 7.5 (BufferA). His-tagged FcγRIIIA/IA protein was captured using Ni-NTA His BindSuperflow resin (Novagen, Madison, Wis.) equilibrated in Buffer A.Elution of bound protein was accomplished using a gradient of imidazole(0-500 mM) in 50 mM NaPO₄, 500 mM NaCl, pH 7.5. Fractions were analyzedfor FcγRIIIA/IA by SDS-PAGE and Western blotting (anti-6× Histidine HRPmouse IgG1, R & D Systems, Minneapolis, Minn.).

The Ni-NTA fractions containing FcγRIIIA/IA-CH6 were buffer-exchangedinto 50 mM NaPO₄, 150 mM NaCl, pH 7.5 (Buffer B) and incubated with QSepharose 4FF resin (GE Healthcare, Uppsala, Sweden) that waspre-equilibrated in Buffer B overnight at 4° C. The slurry wastransferred to a gravity flow column, the flow-through and washfractions were combined and assessed for the presence of rh-FcgR asdescribed above. The combined fractions were concentrated and injectedonto a Superdex 200 Hiload (GE Healthcare, Uppsala, Sweden) columnequilibrated in 50 mM NaPO₄, 109 mM NaCl, pH 7.3 (Buffer C). The columnwas eluted in Buffer C and fractions containing FcγRIIIA/IA-CH6 werecombined, concentrated, sterile-filtered, and stored at −80° C.FcγRIIIA/IA-CH6 was analyzed by SDS-PAGE, Western blotting, N-terminalsequencing, and size exclusion multi-angle light scattering.

Example 21 Aggregation Studies

Aggregation of Soluble Native FcγRIA

Large scale production of soluble recombinant human FcγRIA (CD64A) frommammalian cells has historically been problematic. (See Berntzen et al.,J. Immunol. Methods 298:93-104, 2005; Sondermann and Oosthuizen,Biochem. Soc. Trans. 30:481-486, 2002; Paetz et al., Biochem. Biophys.Res. Commun. 338:1811-1817, 2005; Bruhns et al., Blood DOI 10.1182,2008/blood-2008-09-179754]. The present inventors have discovered thatlow yields of soluble recombinant human FcγRIA from either 293f or CHODXB-11 cells are largely due to temperature-dependent, non-covalentself-association of the protein resulting in large soluble aggregates.Formation of the FcγRIA aggregates, moreover, limits the recovery ofprotein from cell culture conditioned medium. To study the aggregationprocess in greater detail, FcγRIA was purified from the conditionedmedium of CHO DXB-11 cells as described above. The highly-purifiedFcγRIA protein was incubated for various times at 4° C., 25° C. and 37°C. and the formation of aggregates was monitored by size exclusionchromatography on a Superdex 75 column.

The elution profile of FcγRIA, following incubation for up to 48 h ateither 4° C. or 25° C., was identical to that of a freshly-thawed sampleof FcγRIA, i.e., the protein eluted from the column as a singlehomogenous peak with an elution time of 10.3 minutes. Incubation ofFcγRIA for 0, 2, 5, 20, or 48 h at 37° C., in contrast, resulted in atime-dependent reduction in the amount of material eluting as monomericFcγRIA with a quantitative increase in material eluting at 7.8 min, anelution profile consistent with the formation of large FcγRIAaggregates. For samples incubated for 0, 2, 5, 20, or 48 h at 37° C.,the amount of material recovered as aggregate was 0%, 17%, 43%, 83% and93% of the total FcγRIA applied to the column, respectively.

To assess whether aggregated FcγRIA was biologically active, materialincubated at 37° C. for 20 h (83% aggregated) was tested for inhibitionof immune complex precipitation as described previously. (See Ellsworthet al., J. Immunol. 180, 580-589, 2008.) Incubation of a mixture ofovalbumin and anti-ovalbumin with increasing amounts of non-incubated(monomeric) FcγRIA produced a dose-dependent inhibition of immunecomplex precipitation with maximal inhibition observed with 5.0 μMFcγRIA. In contrast, little or no inhibition was observed with identicalconcentrations of aggregated FcγRIA. Similar results were obtained in anIgG-Sepharose elution assay where cell conditioned media or purifiedFcγRIA protein was applied to a small column of IgG-Sepharose. In thisassay, the FcγRIA sample was applied to the column, the column waswashed with PBS and the bound FcγRIA was eluted with low pH buffer. Thewash fractions and the low pH buffer elution were collected and theamount of FcγRIA in the load, wash, and elution fractions was assessedby Western blotting with anti-FcγRIA specific antibodies. For FcγRIAincubated at 37° C. for 48 h, 96% of the total FcγRIA was found in theunbound wash fraction and 4% was in the bound fraction. In contrast, forFcγRIA incubated at 4° C., the entire sample was found in the boundfraction. These data demonstrate that aggregated FcγRIA does not bind toIgG-Sepharose. Taken together, these data demonstrate that aggregatedFcγRIA is biologically inactive.

The temperature-dependent aggregation of FcγRIA appears to beirreversible as the Superdex 75 elution profile of previously aggregatedmaterial was not altered by an additional incubation at 4° C. or 25° C.or by the addition of an excess amount of human IgG1.

Further evidence for a temperature-induced unfolding of FcγRIA came frommeasurements of the circular dichroism (CD) spectra of FcγRIA followingincubation of FcγRIA at 37° C. in phosphate buffer for 0, 5, 10, 15, or20 h. For non-incubated FcγRIA (0 h), two peaks of CD signal wereobserved at approximately 270 nm and 290 nm separated by a trough atabout 285 nm. With FcγRIA incubated for various times at 37° C., atime-dependent decrease in CD signal intensity was observed across thesewavelengths indicating a time- and temperature-dependent loss ofstructure for FcγRIA.

These data were further substantiated by assessing the stability ofFcγRIA in solution by dynamic light scattering (DLS). In DLSexperiments, time-dependent fluctuations in light scattering intensityresulting from molecules diffusing in solution was measured. Changes inlight scattering are related to molecular size and conformation.Diffusion coefficients were measured which were then used to calculatethe hydrodynamic radius (Rh) of FcγRIA. FcγRIA was incubated inphosphate buffer pH 7.3 at 25° C. and 37° C. for various times and theRh was assessed. For non-incubated FcγRIA (0 h) the Rh was ˜3.4 nm. Nochange in the Rh was noted for FcγRIA incubated at 25° C. for variousperiods of time (Rh˜3.2 nm for all incubation times). In contrast, theRh of FcγRIA increased with time of incubation at 37° C. to 4.1 nm, 5.2nm, 6.4 nm, and 12.8 nm for samples incubated for 1.0 h, 2.0 h, 3.0 h,and 48 h, respectively. These data indicate that FcγRIA was eithermultimerizing or unfolding over time at 37° C. in this formulation.

The data described above demonstrated that highly purified FcγRIA wasunstable and formed inactive, self-associated aggregates when incubatedat 37° C. in phosphate buffer at neutral pH. To evaluate whetheraggregation also occurred in the conditioned media of CHO cellsexpressing FcγRIA, undiluted conditioned media from cells maintained at37° C. was evaluated using the IgG-Sepharose binding assay describedabove. For FcγRIA-expressing CHO cells cultured at 37° C., one-dayconditioned media were collected and applied to the IgG-Sepharosecolumn. Eighty percent of the recovered FcγRIA was found in the unboundfraction (aggregated protein) with the remainder (20%) eluting from thecolumn as monomeric FcγRIA. These data indicate that FcγRIA aggregateswithin the conditioned media of CHO cells and likely explains the poorproduction/recovery of recombinant soluble FcγRIA recorded by others.(See Berntzen et al., supra; Sondermann and Oosthuizen, supra; Paetz etal., supra; Bruhns et al., supra.)

Stability Studies of the Hybrid Receptor FcγRIIIA/IA

To circumvent the temperature-induced aggregation of native recombinantsoluble FcγRIA, a hybrid FcγR molecule was generated using adomain-swapping protocol where the membrane distal Ig domain of nativeFcγRIIIA (CD16A) was substituted for the membrane distal Ig domain ofnative FcγRIA using the protocol described above. As noted above, the invitro and in vivo biological activities of the hybrid receptor,FcγRIIIA/IA, was identical to that of native FcγRIA. To assess whetherthe hybrid receptor, FcγRIIIA/IA, was as sensitive totemperature-induced aggregation, native FcγRIA and the hybrid receptor,FcγRIIIA/IA, were each incubated at 37° C. in phosphate buffer, pH 7.3for various lengths of time. Aggregation of each FcγR was monitored bysize exclusion chromatography as described above and the percent of thetotal FcγR present as aggregate was calculated. The percent aggregationof native FcγRIA incubated for 0 h, 2 h, 4 h, 20 h, 24 h, or 48 h at 37°C. was 0, 14%, 40%, 81%, 84%, and 95%, respectively. In contrast, thepercent aggregation for FcγRIIIA/IA incubated under identical conditionswas 0, 2%, 6%, 30%, 34%, and 51%. The difference in aggregation betweennative FcγRIA and FcγRIIIA/IA was even more pronounced in 0.1M succinatebuffer, pH 6.0: the percent aggregation of native FcγRIA incubated for 0h, 2 h, 4 h, 20 h, 24 h, or 48 h was 0, 5%, 13%, 52%, 55%, and 77%,respectively. The percent aggregation of FcγRIIA/IA under theseconditions was 0, 0, 0%, 0%, 5%, 8%, and 16%, respectively. These dataindicate that the hybrid receptor, FcγRIIIA/IA, in much less susceptibleto temperature-induced aggregation than native FcγRIA.

Similar data were obtained by dynamic light scattering (DLS) analysis ofFcγRIIA/IA under conditions identical to those described above fornative FcγRIA. In contrast to the increase in Rh of native FcγRIAfollowing incubation of the protein at 37° C., no change in hydrodynamicradius (Rh) was observed for FcγRIIIA/IA after incubation at 37° C. forup to 3.0 h (Rh=3.6-3.8 over these times). A small increase in Rh, to5.1 nm, was seen for FcγRIIIA/IA incubated at 37° C. for 48 h. Asdescribed above, this increase in Rh was much less than that observedfor native FcγRIA incubated under identical conditions were the Rhincreased to 12.8 nm. Again, these data demonstrate that the hybridreceptor FcγRIIIA/IA is less susceptible to temperature-inducedaggregation compared with native FcγRIA.

To assess whether recovery of monomeric FcγRIIIA/IA in CHO conditionedmedia was increased relative to that of native FcγRIA, the amount ofmonomeric and aggregated FCGR in 24 h cultures of CHO cells expressingeach of these receptors was compared. Aggregation was monitored usingthe IgG-Sepharose binding assay with detection by Western blotting asdescribed above. As a percent of the total FcγR applied to the column,53% of FcγRIIIA was monomeric in that it bound to IgG-Sepharose and waseluted in the low pH wash step, while 47% of the protein eluted in thewash as aggregated material. In contrast, for native FcγRIA, only 14% ofthe protein bound to IgG-Sepharose with 86% of the protein eluted in thewash as aggregated material. As with the pure protein, these dataindicate that FcγRIIA/IA is less susceptible to temperature-inducedaggregation in CHO-conditioned media and can be recovered in increasedamounts relative to native FcγRIA.

Example 22 Comparison of Anti-Inflammatory Activities of Soluble FcγRIA,FcγRIIA/RIA, and FcγRIIIA/IA

Methods

1. Immune Complex Precipitation

Chicken egg ovalbumin (OVA) was dissolved to a final concentration of15.0 μg/mL in phosphate buffered saline (PBS) and combined with 300 μgrabbit polyclonal anti-OVA antibodies/mL in a final volume of 200 μL inthe presence and absence of the indicated concentration of native FcγRIAsoluble receptor or one of the hybrid soluble receptors, FcγRIIA/IA-CH6or FcγRIIIA/IA-CH6 (also referred to in this Example as “FcγRIIA/IA” (or“FCGR2A1A”) and “FcγRIIIA/IA” (or “FCGR3A1A”), respectively).Immediately thereafter, turbidity of the reaction mixture was monitoredat 350 mm every 30 seconds for 5-10 min at 37° C. with the aid of aspectrophotometer. Linear regression was used to calculate the slope ofthe linear portion of the turbidity curves and the FcγR-mediatedinhibition of immune complex precipitation was expressed relative toincubations containing anti-OVA and OVA alone.

2. Cytokine Secretion from Mast Cells

Immune complexes were prepared by mixing 300 μL of rabbit polyclonalanti-OVA with 75.0 μL of 1 mg OVA/mL in PBS in a final volume of 5.0 mLof PBS. After incubation at 37° C. for 30-60 min, the mixture was placedat 4° C. for 18-20 h. The immune complexes were collected bycentrifugation at 12,000 rpm for 5.0 min, the supernatant fraction wasremoved and discarded, and the immune complex precipitate wasresuspended 1.0 mL of ice cold PBS. After another wash, the immunecomplexes were resuspended in a final volume of 1.0 mL ice cold PBS.Protein concentration was determined using the BCA assay.

MC/9 cells were sub-cultured in Medium A (DMEM containing 10% fetalbovine serum, 50.0 μM B-mercaptoethanol, 0.1 mM non-essential aminoacids, 1.0 mM sodium pyruvate, 36.0 μg/mL L-asparagine, 1.0 ng/mLrmIL-3, 5.0 ng/mL rmIL-4, 25.0 ng/mL rmSCF) to a density of 0.5−3×10⁶cells/mL. Cells were collected by centrifugation at 1500 rpm for 5.0 minand the cell pellet was washed in Medium A (without cytokines) andresuspended in Medium A at 2.0×10⁶ cells/mL. Aliquots of cells (2.0×10⁵cells) were incubated with 10.0 μg/well of OVA/anti-OVA immune complexes(IC's) in a final volume of 200 μL of Buffer A in a 96-well microtiterplate in the presence and absence of the indicated concentration ofnative FcγRIA soluble receptor or one of the hybrid soluble receptors,FcgRIIA/IA-CH6 or FcgRIIA/IA-CH6. After 4.0 h at 37° C., the media wasremoved and centrifuged at 1500 rpm for 5.0 min. The cell-freesupernatant fractions were collected and aliquots were analyzed for thepresence of IL-6, IL-13, TNFα, and MCP-1 cytokine release using aLuminex cytokine assay kit.

3. Measurement of FcγR Affinity for Human IgG1

The IgG1 antibody was immobilized to a single flow cell, utilizing asecond non-derivatized cell as the blank reference. Immobilization ofthe IgG1 antibody was performed using an amine coupling kit (Biacore)and the standard Wizard Template for Surface Preparation, operated bythe Biacore Control Software. Based on Wizard results for a pH scoutingstudy, the IgG1 antibody solution was diluted to 11 μg/mL in sodiumacetate, pH 5.0. The Wizard Template for amine coupling was used toimmobilize the antibody to a single flow cell. The carboxyl groups onthe sensor surfaces were then activated with an injection of a solutioncontaining 0.2 M N-ethyl-N′-(3-diethylamino-propyl) carbodiimide (EDC)and 0.05 M N-hydroxysuccinimide (NHS). The antibody solution was theninjected over the activated surface targeting a level of 150-200 RU. Theimmobilization procedure was completed by blocking remaining ester siteson the carboxymethyl dextran surface with 1 M ethanolaminehydrochloride.

The method for injection of the analyte solutions (soluble native FcγRIAor the soluble hybrid receptors, FcγRIIA/IA and FcγRIIIA/IA) was writtenusing the Biacore Wizard Template for kinetic analysis. The method wasrun at 25° C. and the samples stored in the autosampler at ambienttemperature. It is noted that in using the Wizard Template, certainparameters optimal for kinetics, such as injection modes, arepre-defined by the Wizard program.

The method for analysis of soluble FcγRIA was optimized fordetermination of kinetic rate constants, k_(a) and k_(d). The receptorwas injected over both flow cells (i.e., 1 and 2, blank andantibody-derivatized, respectively) in series to allow for comparativeanalysis of binding of the FcγR to the human IgG1 antibody vs. bindingof the FcγR to the non-modified control surface (binding to rabbitanti-OVA IgG not tested). The analyte was injected at a flow rate of 40L/min for 3 minutes (association time). The dissociation time for eachanalyte injection was 3 minutes. The analyte dose response curve rangewas 0.16-10.3 nM. For each dose response curve point, N=2 replicateinjections were run. The sequence included injections of buffer forsubtraction of instrument noise and drift. Dose response curve sampleswere injected in random mode. For kinetic analysis of FcγR, each doseresponse curve cycle was followed by a single 30 second injection ofglycine, pH 1.75 at 50 μL/minute to regenerate the IgG antibody surface.

Data analysis was performed using Biacore Control, Evaluation andSimulation software. Baseline stability was first assessed to ensurethat the regeneration step provided a consistent binding surfacethroughout the sequence of injections. The level of non-specific bindingof the FcγR analyte to the control surface was checked and confirmed tobe minimal. Binding curves were processed by subtraction of the controlsurface curve (i.e., flow cell 1) from the specific binding surfacecurve (i.e., flow cell 2), as well as subtraction of instrument noiseand drift using a buffer injection curve. The data was checked forreproducibility of analyte injections and the resulting correctedbinding curves were then globally fitted to binding models and theresulting fit and equilibrium constants evaluated.

4. Cutaneous Reverse Passive Arthus Reaction in Mice

Ten-week old female C57BL/6 mice (n=8 mice per group) were anesthetizedwith isoflurane, their dorsal skin was shaved, and the back of eachmouse was wiped with 70% alcohol. Each mouse received two intradermalinjections of 0.02 mL each, at distinct sites in the dorsal skin. Theinjection solutions contained phosphate buffered saline (PBS) and either40.0 μg of rabbit anti-ovalbumin (anti-OVA, heat-inactivated byincubation at 56° C. for 30-40 min) alone or 40.0 μg of anti-OVA and theindicated amount of soluble native FcγRIA or one of the soluble hybridreceptors, FcγRIIA/IA or FcγRIIIA/IA. Mice in the control groupsreceived two intradermal injections of 40.0 μg non-immune rabbit IgG(heat-inactivated as described above). Antibody preparations werecentrifuged at 14,000 rpm for 10 min to remove particulates prior toinjection. Immediately following the intradermal injections, each mousewas injected in the tail vein with 100.0 μL of a solution containing10.0 mg OVA/mL and 10.0 mg Evan's Blue/mL. In some instances, the tailvein injection solution also contained dexamethazone at a dose of 1.0mg/kg. Four hours after the injections, the mice were euthanized by CO₂gas. Cutaneous edema was evaluated by measuring the area of vascularleak of Evan's Blue dye (mm²) and by measuring tissue weights (mg) ofpunch biopsies taken from the lesion sites. The tissue samples were thenquickly frozen in liquid N₂ and stored at −80° C.

Neutrophil infiltration was assessed by measuring myeloperoxidaseactivity in the punch biopsy samples as described (see Bradley et al.,J. Invest. Dermatol. 78:206-209, 1982) using the Myeloperoxidase AssayKit from Cytostore (Calgary, Alberta Canada).

Results and Discussion

To evaluate the relative efficacy of native FcγRIA soluble receptor andthe hybrid FcγR soluble receptors, FcγRIA/1A and FcγRIIIA/IA, on immunecomplex precipitation, an anti-OVA/OVA immune complex precipitationassay was established based on the methods of MØller (Immunology38:631-640, 1979) and Gavin et al., (Clin. Exp. Immunol. 102:620-625,1995). Incubation of anti-OVA and OVA at 37° C. produced atime-dependent increase in optical density of the solution mixture, anobservation consistent with the formation of insoluble anti-OVA/OVAimmune complexes. Addition of soluble native FcγRIA at the start of theassay produced a dose-dependent reduction in optical density of themixtures indicating an inhibition of immune complex precipitation.Immune complex precipitation was completely abolished by 1500 nM solubleFcγRIA. Similarly, both soluble hybrid receptors, FcγRIIA/IA andFcγRIIIA/IA, blocked precipitation of OVA-anti-OVA immune complexes. Thedose response curves were similar for all three FcγR, indicating thatthe receptors had equal potency. Since the precipitation ofantigen:antibody immune complexes appears to be dependent onnon-covalent interactions between the antibody Fc heavy chains (MØller,Immunology 38:631-640, 1979) and Fcγ receptors bind to the Fc portion ofantibodies (Dijstelbloem et al., Trends Immunol. 22, 510-516, 2001),these data suggest that soluble native FcγRIA and the soluble hybridreceptors, FcγRIIA/IA and FcγIIIA/IA, disrupt immune complexprecipitation by binding to the Fc portion of the anti-OVA antibodies.

To directly evaluate the interaction of native FcγRIA and each hybridreceptor with antibody Fc, the binding of FcγR to immobilized human IgG1was assessed by surface plasmon resonance analyses. A monoclonal humanIgG1 antibody was immobilized to the sensor surface in a single flowcell at an RU (resonance units) level of 485, a density level withinoptimal levels for kinetic analysis of FcγR, presuming a bindingstoichiometry of one FcγR molecule with one IgG1 molecule (Woof andBurton, Nature Rev. Immunol. 4:1-11, 2004). Native FcγRIA solublereceptor rapidly bound to immobilized IgG1 with rates of association anddissociation of 2.8×10⁶ M⁻¹s⁻¹ and 4.6×10⁻⁴ s⁻¹, respectively, valueswhich yield a calculated equilibrium dissociation constant of 1.7×10⁻¹⁰M. These data are similar to those reported previously (Paetz et al.,Biochem. Biophys. Res. Commun. 338:1811-1817, 2005) and demonstrate thatsoluble native FcγRIA binds with high affinity to human IgG1. Thesoluble hybrid receptors, FcγRII/IA and FcγRIIIA/IA, rapidly bound toimmobilized IgG1 with rates of association and dissociation similar tothat of native FcγRIA. These data indicate that the hybrid receptorsbound to immobilized human IgG1 with high affinity.

Mast cells are thought to mediate immune complex-mediated inflammationin a variety of immune disorders such as type III hypersensitivityreactions (Ravetch, J. Clin. Invest. 110:1759-1761, 2002; Sylvestre andRavetch, Immunity 5:387-390, 1996; Jancar and Crespo, Trends Immunology26:48-55, 2005). Binding of immune complexes to mast cell Fcγ receptorsis thought to induce the secretion of pro-inflammatory cytokines, suchas IL-6 and TNFα (Ravetch, supra; Jancar and Crespo, supra), whichsubsequently leads to neutrophil infiltration and tissue damage. Toevaluate whether cytokine secretion from mast cells could be stimulatedby immune complexes, the murine mast cell line MC/9 was incubated in thepresence and absence of preformed rabbit anti-OVA/OVA immune complexes.Incubation with anti-OVA/OVA immune complexes produced a time andconcentration dependent increase in the accumulation of the inflammatorycytokines IL-6, IL-13, TNFα, and MCP-1 within the MC/9 cell conditionedmedia. Cytokine production was not altered, in contrast, when MC/9 cellswere incubated with an equivalent concentration of rabbit anti-OVA IgGalone. These data demonstrate that MC/9 cells respond to immunecomplexes by the production of inflammatory cytokines.

Incubation of MC/9 cells with anti-OVA/OVA immune complexes in thepresence of increasing amounts of native FcγRIA soluble receptor or oneof the hybrid soluble receptors, FcγRIIA/IA or FcγRIIIA/IA, produceddose-dependent reductions in the accumulation of IL-6, IL-13, TNFα, andMCP-1 (see FIG. 13). Little or no differences in the dose responsecurves for each receptor was noted, indicating identical potencies foreach of the receptors. These data demonstrate that native FcγRIA and thehybrid soluble receptors can block the binding and signalling of immunecomplexes in mouse mast cells.

The findings described above demonstrate that soluble native FcγRIA andthe soluble hybrid receptors, FcγRIIA/IA and FcγRIIIA/IA, can block theformation of immune complexes in vitro and can inhibit immunecomplex-mediated signaling in mast cells. These data suggest that theFcγR may be effective at blocking immune complex-mediated inflammationin an in vivo setting. To test this, the cutaneous reversed passiveArthus reaction was established in mice and the effects of each of theFcγR on immune complex-mediated edema and neutrophil infiltration wereassessed.

Relative to intradermal injection of an equivalent concentration ofnonimmune IgG, injection of anti-OVA antibodies produced a time andconcentration increase in edema within the skin of treated mice. Edemawas evident as both an increase in the area of extravasation of Evan'sblue dye and in tissue weights. These effects were specific for immunecomplexes as no edema was observed in the absence of tail vein injectionof OVA. Accumulation of neutrophils within the lesion site, measured byextractable activity of myeloperoxidase, was also increased.

Intradermal delivery of anti-OVA antibodies with increasing amounts ofsoluble native FcγRIA produced a concentration-dependent reduction inedema, measured by either a decrease in Evan's blue area (FIGS. 14A and15A) or a decrease in tissue weight of the lesion site (FIGS. 14B and15B). Similar results were obtained using either of the soluble hybridreceptors, FcγRIIA/IA (FIGS. 14A and 14B) and FcγRIIIA/IA (FIGS. 15A and15B).

Both hybrid receptors reduced both measures of edema and were equipotentrelative to native FcγRIA. Neutrophil infiltration, as measured bymyeloperoxidase activity in the lesion biopsies, was also significantlydecreased by soluble native FcγRIA and each soluble hybrid receptor withequivalent potencies (FIGS. 16A and 16B). These results show thatsoluble native FcγRIA and each soluble hybrid receptor, FcγRIIA/IA andFcγRIIIA/IA, can block edema and neutrophil infiltration in the reversepassive Arthus reaction in mice.

Although the foregoing invention has been described in detail forpurposes of clarity of understanding, it will be appreciated thatcertain modifications may be practiced within the scope of the appendedclaims. All publications and patent documents cited herein are herebyincorporated by reference in their entirety for all purposes to the sameextent as if each were so individually denoted.

What is claimed is:
 1. An isolated, soluble polypeptide comprising anamino acid sequence selected from the group consisting of amino acidresidues 43-310 of SEQ ID NO:42; amino acid residues 21-286 of SEQ IDNO:44; and amino acid residues 21-286 of SEQ ID NO:46; wherein saidpolypeptide is capable of specifically binding the Fc region of IgG. 2.The polypeptide of claim 1, further comprising a secretory signalsequence.
 3. A composition comprising: an isolated polypeptide as inclaim 1; and a pharmaceutically acceptable vehicle.